fix(ci): bump actions/cache version

Author: mavi0

.github/workflows/elixir.yml

@@ -26,7 +26,7 @@ jobs:
         otp-version: '24' # 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') }}