bump actions to cache@v3

 mn/#3-support-latest-elasticsearch-dsl-6

.github/workflows/ci.yml

@@ -66,7 +66,7 @@ jobs:
           python-version: ${{ matrix.python-version }}
 
       - name: Cache Pip Dependencies
-        uses: actions/cache@v2
+        uses: actions/cache@v3
         with:
           path: ~/.cache/pip
           key: ${{ runner.os }}-pip-${{ hashFiles('requirements/test.txt') }}