fix: disable latest tag for Alpine image

Only standard/main image variant should use the latest tag. The Alpine image
should only have its version-specific tags.

Author: vkartk

.github/workflows/build-docker-image-alpine.yml

@@ -71,6 +71,8 @@ jobs:
           images: |
             ghcr.io/${{ env.REPO_OWNER }}/caddy-cloudflare
             ${{ secrets.DOCKERHUB_USERNAME }}/caddy-cloudflare
+          flavor: |
+            latest=false
           tags: |
             # Raw version tags
             type=raw,value=${{ env.VERSION }}-alpine