FIX: Add pytestonwindows matrix entry to clear stale CodeQL snapshot SM02986 (#417)

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[AB#41680](https://sqlclientdrivers.visualstudio.com/c6d89619-62de-46a0-8b46-70b92a84d85e/_workitems/edit/41680)

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### Summary   
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This pull request adds a temporary entry to the job matrix in
`eng/pipelines/pr-validation-pipeline.yml` to help clear a stale CodeQL
snapshot. This is a short-term workaround and should be removed once the
underlying issue is resolved.

Pipeline configuration:

* Added a `pytestonwindows` entry to the job matrix, specifying
`sqlVersion: 'SQL2022'` and `pythonVersion: '3.13'`, to clear a stale
CodeQL snapshot (SM02986).

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Author: gargsaumya

eng/pipelines/pr-validation-pipeline.yml

@@ -56,6 +56,11 @@ jobs:
 
   strategy:
     matrix:
+      pytestonwindows:
+        # Temporary entry to clear stale CodeQL snapshot SM02986
+        # Remove this once the issue is resolved
+        sqlVersion: 'SQL2022'
+        pythonVersion: '3.13'
       SQLServer2022:
         sqlVersion: 'SQL2022'
         pythonVersion: '3.13'