chore: run the Codebuild build on every PR, no matter the target branch (#35042)

Otherwise, builds won't run on stacked PRs.

----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

Author: otaviomacedo

.github/workflows/codebuild-pr-build.yml

@@ -7,10 +7,7 @@ on:
     branches:
       - main
       - v2-release
-  pull_request:
-    branches:
-      - main
-      - v2-release
+  pull_request: {}
 
 # For every PR, cancel any previous builds in progress
 # ... but for all other builds we keep them running