docker.yml: Set latest to auto to tag release version (#3581)

.github/workflows/docker.yml

@@ -19,7 +19,7 @@ jobs:
         uses: docker/metadata-action@v5
         with:
           images: ghcr.io/${{ github.repository_owner }}/xray-core
-          flavor: latest=true
+          flavor: latest=auto
           tags: |
             type=sha
             type=ref,event=branch