fix: install compose through docker and not python (#18)

Author: Naramsim

updater/Dockerfile

@@ -5,7 +5,7 @@ RUN apk add curl python3 git bash dos2unix openssh build-base python3-dev
 
 RUN ln -sf $(ls /usr/bin/easy_install*) /usr/bin/easy_install
 RUN easy_install pip
-RUN pip install docker-compose
+COPY --from=docker/compose:1.25.0-alpine /usr/local/bin/docker-compose /usr/local/bin/
 
 RUN mkdir /updater
 WORKDIR /updater