Update docker/setup-buildx-action action to v4

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

Author: renovate[bot]

.github/workflows/axoverlay2.yml

@@ -20,7 +20,7 @@ jobs:
       EXNAME: axoverlay2
     steps:
       - uses: actions/checkout@v6
-      - uses: docker/setup-buildx-action@v3
+      - uses: docker/setup-buildx-action@v4
 
       - name: Build ${{ env.EXNAME }} application
         env: