Use actions/cache@v4 in the github workflow

Author: Gleb Ivanov

.github/workflows/ci.yml

@@ -69,7 +69,7 @@ jobs:
           otp-version: ${{matrix.pair.otp}}
           elixir-version: ${{matrix.pair.elixir}}
 
-      - uses: actions/cache@v2
+      - uses: actions/cache@v4
         with:
           path: |
             deps