chg: Add cache in GHA

.github/workflows/instance_test.yml

@@ -21,6 +21,7 @@ jobs:
         uses: actions/setup-python@v4
         with:
           python-version: ${{matrix.python-version}}
+          cache: 'pip'
 
       - name: Install and setup redis
         run: |

.github/workflows/mypy.yml

@@ -20,6 +20,7 @@ jobs:
       uses: actions/setup-python@v4
       with:
         python-version: ${{matrix.python-version}}
+        cache: 'pip' # caching pip dependencies
 
     - name: Install dependencies
       run: |