ci: Update actions/cache to v4

Github has deprecated v2 so this needs to be bumped.

Author: tgross35

.github/workflows/main.yml

@@ -117,7 +117,7 @@ jobs:
       with:
         key: ${{ matrix.target }}
     - name: Cache Docker layers
-      uses: actions/cache@v2
+      uses: actions/cache@v4
       if: matrix.os == 'ubuntu-latest'
       with:
         path: /tmp/.buildx-cache