fix container name

Author: hiroyaonoe

.github/workflows/docker.yaml

@@ -36,7 +36,7 @@ jobs:
         with:
           context: .
           push: true
-          tags: ghcr.io/picop-rd/proxy/proxy:latest
+          tags: ghcr.io/picop-rd/proxy:latest
           cache-from: type=gha
           cache-to: type=gha,mode=max
           ssh: default