Update docker/setup-buildx-action digest to c8ad1c5

Author: renovate[bot]

.github/workflows/build-publish.yml

@@ -54,7 +54,7 @@ jobs:
 
       # Workaround: https://github.com/docker/build-push-action/issues/461
       - name: Setup Docker buildx
-        uses: docker/setup-buildx-action@1583c0f09d26c58c59d25b0eef29792b7ce99d9a
+        uses: docker/setup-buildx-action@c8ad1c5d0f6f39c2bc446b807fa8ea2afadcddb6
 
       # Login against a Docker registry except on PR
       # https://github.com/docker/login-action