Update actions/cache@v2 -> v4 in ci.yml

Author: nelsonic

.github/workflows/ci.yml

@@ -29,7 +29,7 @@ jobs:
           elixir-version: "1.14.2" # Define the elixir version [required]
           otp-version: "25.1.2" # Define the OTP version [required]
       - name: Restore dependencies cache
-        uses: actions/cache@v2
+        uses: actions/cache@v4
         with:
           path: deps
           key: ${{ runner.os }}-mix-${{ hashFiles('**/mix.lock') }}