chore: update github actions cache from v2 to v4

.github/workflows/mysql8-migrations.yml

@@ -35,7 +35,7 @@ jobs:
         echo "dir=$(pip cache dir)" >> $GITHUB_OUTPUT
     - name: Cache pip dependencies
       id: cache-dependencies
-      uses: actions/cache@v2
+      uses: actions/cache@v4
       with:
         path: ${{ steps.pip-cache-dir.outputs.dir }}
         key: ${{ runner.os }}-pip-${{ hashFiles('requirements/pip-tools.txt') }}