Update GitHub Actions workflow to include sparse checkout for run_tests action

This commit enhances the GitHub Actions workflow by adding the `run_tests` action to the sparse checkout configuration. This change ensures that the necessary files for running tests are included in the checkout process, improving the workflow's efficiency and reliability.

Key changes:
- Added `.github/actions/run_tests/` to the sparse checkout list.

Author: naspirato

.github/workflows/run_tests.yml

@@ -93,6 +93,7 @@ jobs:
         with:
           sparse-checkout: |
             .github/config/stable_branches.json
+            .github/actions/run_tests/
 
       - name: Set branches
         id: set-branches