refactor: update to zrx to v0.0.21

Signed-off-by: squidfunk <martin.donath@squidfunk.com>

.github/workflows/build.yml

@@ -288,7 +288,7 @@ jobs:
           buildkitd-flags: --debug
 
       - name: Build image
-        uses: docker/build-push-action@v6
+        uses: docker/build-push-action@v7
         with:
           context: .
           load: true

.github/workflows/commit.yml

@@ -38,7 +38,7 @@ jobs:
       - name: Checkout repository
         uses: actions/checkout@v6
         with:
-          ref: ${{ github.event.pull_request.base.sha }}
+          ref: ${{ github.event.pull_request.head.sha }}
           fetch-depth: 0
 
       - name: Set up mono