Disable the merge queue (#6780)

## Summary of changes

Disables the merge queue

## Reason for change

We don't want it.

It hits our CI very hard and doesn't work very well for us, we prefer to
use the manual button to merge the PRs

## Implementation details

Added the file, also saw that
https://github.com/DataDog/dd-trace-go/blob/main/repository.datadog.yml
has it as well so I think this should be good.

## Test coverage

None

## Other details
<!-- Fixes #{issue} -->

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Author: bouwkast

repository.datadog.yml

@@ -0,0 +1,4 @@
+---
+schema-version: v1
+kind: mergequeue
+enable: false