ci: update cache key

Author: tsirysndr

.github/workflows/ci.yml

@@ -25,7 +25,7 @@ jobs:
         uses: actions/cache@v3
         with:
           path: /tmp/.buildx-cache
-          key: ${{ runner.os }}-buildx-${{ hashFiles('**/Dockerfile') }}
+          key: ${{ runner.os }}-buildx
 
       - name: Build and Publish image
         uses: fluentci-io/setup-fluentci@v5