update actions/cache version

Author: micaelaw

.github/workflows/CI.yml

@@ -26,7 +26,7 @@ jobs:
         python-version: ${{ matrix.python-version }}
 
     - name: Cache pip
-      uses: actions/cache@v2
+      uses: actions/cache@v3
       with:
         # This path is specific to Ubuntu
         path: ~/.cache/pip