Update docker/build-push-action digest to 31ca4e5

Author: renovate[bot]

.github/workflows/docker.yml

@@ -54,7 +54,7 @@ jobs:
 
       - name: Build and push Docker image
         id: push
-        uses: docker/build-push-action@b32b51a8eda65d6793cd0494a773d4f6bcef32dc
+        uses: docker/build-push-action@31ca4e5d51253d7e4a2317bfe74699cbe3a398a9
         with:
           context: .
           file: ${{ matrix.dockerfile }}