Ensure that the valid and default strategies are up-to-date and accur…

…ate per adapter (#4638)

resolves #4633


[Preview](https://docs-getdbt-com-git-dbeatty-update-incremental-4cfb6d-dbt-labs.vercel.app/docs/build/incremental-models#supported-incremental-strategies-by-adapter)

## What are you changing in this pull request and why?

- `merge` has been the default since [dbt-databricks
1.0.0](https://github.com/databricks/dbt-databricks/blob/7ad5507a8a38bde682bb28eb37466bbfc341ac94/CHANGELOG.md?plain=1#L404)
- For readability, removing references to "Delta only" since those were
added in [#77](#77)
(April 2020) and not updated since then to reflect additions of Hudi and
Iceberg
- Opened
[#4639](#4639) to
follow-up on the details

## 🎩 

<img width="450" alt="image"
src="https://github.com/dbt-labs/docs.getdbt.com/assets/44704949/016e098a-fc45-4841-9ce2-db2ad5049af5">

## Checklist
- [x] Review the [Content style
guide](https://github.com/dbt-labs/docs.getdbt.com/blob/current/contributing/content-style-guide.md)
so my content adheres to these guidelines.

website/docs/docs/build/incremental-models.md

@@ -255,10 +255,10 @@ The `merge` strategy is available in dbt-postgres and dbt-redshift beginning in
 | [dbt-postgres](/reference/resource-configs/postgres-configs#incremental-materialization-strategies) | `append`         | `delete+insert`                          |
 | [dbt-redshift](/reference/resource-configs/redshift-configs#incremental-materialization-strategies) | `append`         | `delete+insert`                          |
 | [dbt-bigquery](/reference/resource-configs/bigquery-configs#merge-behavior-incremental-models)      | `merge`          | `insert_overwrite`                       |
-| [dbt-spark](/reference/resource-configs/spark-configs#incremental-models)                           | `append`         | `merge` (Delta only)  `insert_overwrite` |
-| [dbt-databricks](/reference/resource-configs/databricks-configs#incremental-models)                 | `append`         | `merge` (Delta only) `insert_overwrite`  |
+| [dbt-spark](/reference/resource-configs/spark-configs#incremental-models)                           | `append`         | `merge`, `insert_overwrite`              |
+| [dbt-databricks](/reference/resource-configs/databricks-configs#incremental-models)                 | `merge`          | `append`, `insert_overwrite`             |
 | [dbt-snowflake](/reference/resource-configs/snowflake-configs#merge-behavior-incremental-models)    | `merge`          | `append`, `delete+insert`                |
-| [dbt-trino](/reference/resource-configs/trino-configs#incremental)                                  | `append`         | `merge` `delete+insert`                  |
+| [dbt-trino](/reference/resource-configs/trino-configs#incremental)                                  | `append`         | `merge`, `delete+insert`                 |
 
 </VersionBlock>
 
@@ -267,13 +267,13 @@ The `merge` strategy is available in dbt-postgres and dbt-redshift beginning in
 
 | data platform adapter  | default strategy | additional supported strategies  |
 | :----------------- | :----------------| : ---------------------------------- |
-| [dbt-postgres](/reference/resource-configs/postgres-configs#incremental-materialization-strategies) | `append`         | `merge` , `delete+insert`                  |
-| [dbt-redshift](/reference/resource-configs/redshift-configs#incremental-materialization-strategies) | `append`         | `merge`, `delete+insert`                  |
+| [dbt-postgres](/reference/resource-configs/postgres-configs#incremental-materialization-strategies) | `append`         | `merge` , `delete+insert`                |
+| [dbt-redshift](/reference/resource-configs/redshift-configs#incremental-materialization-strategies) | `append`         | `merge`, `delete+insert`                 |
 | [dbt-bigquery](/reference/resource-configs/bigquery-configs#merge-behavior-incremental-models)      | `merge`          | `insert_overwrite`                       |
-| [dbt-spark](/reference/resource-configs/spark-configs#incremental-models)                           | `append`         | `merge` (Delta only)  `insert_overwrite` |
-| [dbt-databricks](/reference/resource-configs/databricks-configs#incremental-models)                 | `append`         | `merge` (Delta only) `insert_overwrite`  |
+| [dbt-spark](/reference/resource-configs/spark-configs#incremental-models)                           | `append`         | `merge`, `insert_overwrite`              |
+| [dbt-databricks](/reference/resource-configs/databricks-configs#incremental-models)                 | `merge`          | `append`, `insert_overwrite`             |
 | [dbt-snowflake](/reference/resource-configs/snowflake-configs#merge-behavior-incremental-models)    | `merge`          | `append`, `delete+insert`                |
-| [dbt-trino](/reference/resource-configs/trino-configs#incremental)                                  | `append`         | `merge` `delete+insert`                  |
+| [dbt-trino](/reference/resource-configs/trino-configs#incremental)                                  | `append`         | `merge`, `delete+insert`                 |
 
 </VersionBlock>