hotfix: fix dockerfile typo

* ARG -> ENV

Dockerfile

@@ -33,7 +33,7 @@ ARG NEXT_PUBLIC_KAKAO_API_KEY
 ENV NEXT_PUBLIC_SERVER_URL=${NEXT_PUBLIC_SERVER_URL}
 ENV NEXTAUTH_SECRET=${NEXTAUTH_SECRET}
 ENV NEXTAUTH_URL=${NEXTAUTH_URL}
-ARG NEXT_PUBLIC_KAKAO_API_KEY=${NEXT_PUBLIC_KAKAO_API_KEY}
+ENV NEXT_PUBLIC_KAKAO_API_KEY=${NEXT_PUBLIC_KAKAO_API_KEY}
 
 # Set node environment to production
 ENV NODE_ENV=production