actions: update cache to v4

Fixes:

```
Node.js 16 actions are deprecated.
Please update the following actions to use Node.js 20: actions/cache@v3.
```

Signed-off-by: Sandro Bonazzola <sandro.bonazzola@gmail.com>

Author: sandrobonazzola

.github/workflows/build.yml

@@ -31,7 +31,7 @@ jobs:
       uses: ovirt/checkout-action@main
 
     - name: Use cache for maven
-      uses: actions/cache@v3
+      uses: actions/cache@v4
       with:
         path: ~/.m2/repository
         key: ${{ runner.os }}-maven-${{ hashFiles('**/pom.xml') }}