Editorial polish for registry metrics note

Use parallel "per source" phrasing in the table, switch the v1.4.3
admonition to :::warning since it documents a breaking change to user
queries, and align terminology on "label" to match the table header.

Author: github-actions[bot]

docs/toolhive/guides-registry/telemetry-metrics.mdx

@@ -79,18 +79,18 @@ identification.
 
 ### Available metrics
 
-| Metric                                      | Type          | Labels                           | Description                               |
-| ------------------------------------------- | ------------- | -------------------------------- | ----------------------------------------- |
-| `thv_reg_srv_http_request_duration_seconds` | Histogram     | `method`, `route`, `status_code` | Duration of HTTP requests                 |
-| `thv_reg_srv_http_requests_total`           | Counter       | `method`, `route`, `status_code` | Total number of HTTP requests             |
-| `thv_reg_srv_http_active_requests`          | UpDownCounter | -                                | Number of in-flight requests              |
-| `thv_reg_srv_servers_total`                 | Gauge         | `source`                         | Number of distinct servers in each source |
-| `thv_reg_srv_skills_total`                  | Gauge         | `source`                         | Number of distinct skills in each source  |
-| `thv_reg_srv_sync_duration_seconds`         | Histogram     | `registry`, `success`            | Duration of sync operations               |
-
-:::note
-
-In Registry Server v1.4.3, the attribute on `thv_reg_srv_servers_total` and
+| Metric                                      | Type          | Labels                           | Description                   |
+| ------------------------------------------- | ------------- | -------------------------------- | ----------------------------- |
+| `thv_reg_srv_http_request_duration_seconds` | Histogram     | `method`, `route`, `status_code` | Duration of HTTP requests     |
+| `thv_reg_srv_http_requests_total`           | Counter       | `method`, `route`, `status_code` | Total number of HTTP requests |
+| `thv_reg_srv_http_active_requests`          | UpDownCounter | -                                | Number of in-flight requests  |
+| `thv_reg_srv_servers_total`                 | Gauge         | `source`                         | Number of servers per source  |
+| `thv_reg_srv_skills_total`                  | Gauge         | `source`                         | Number of skills per source   |
+| `thv_reg_srv_sync_duration_seconds`         | Histogram     | `registry`, `success`            | Duration of sync operations   |
+
+:::warning
+
+In Registry Server v1.4.3, the label on `thv_reg_srv_servers_total` and
 `thv_reg_srv_skills_total` was renamed from `registry` to `source`. If you have
 existing Grafana queries, Prometheus alerts, or dashboards that reference the
 `registry` label on these two metrics, switch them to `source`. The