Update docker/setup-buildx-action action to v3.8.0 (#430)

| datasource  | package                    | from   | to     |
| ----------- | -------------------------- | ------ | ------ |
| github-tags | docker/setup-buildx-action | v3.7.1 | v3.8.0 |

Signed-off-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>
Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.github/workflows/ci.yml

@@ -69,7 +69,7 @@ jobs:
           sed -i 's|\${NGINX_PLUS_VERSION}/||g' docker/Dockerfile
 
       - name: Set up Docker Buildx
-        uses: docker/setup-buildx-action@c47758b77c9736f4b2ef4073d4d51994fabfe349 # v3.7.1
+        uses: docker/setup-buildx-action@6524bf65af31da8d45b59e8c27de4bd072b392f5 # v3.8.0
 
       - name: Build Plus Docker Image
         uses: docker/build-push-action@48aba3b46d1b1fec4febb7c5d0c644b249a11355 # v6.10.0