test: Pin pylint to a specific version in GitHub Actions

This should prevent us from failing new pylint rules without any code
changes on our part.

Change-Id: If8b8c2a180e921cdfc3b99a9e17a798599ebe19b

.github/workflows/custom-actions/lint-packager/action.yaml

@@ -18,7 +18,7 @@ runs:
         rm git-clang-format
         echo "::endgroup::"
         echo "::group::Installing pylint"
-        python3 -m pip install --upgrade pylint
+        python3 -m pip install --upgrade pylint==2.8.3
         echo "::endgroup::"
         echo "::group::Check clang-format for C++ sources"
         # NOTE: --binary forces use of global clang-format (which works) instead