Dockerfile: shorter code

Dockerfile

@@ -1,19 +1,12 @@
 FROM monica:apache
 
-RUN apt-get update && \
-  apt-get full-upgrade -y && \
-  rm -rf /var/lib/apt/lists/*
-
 # Use the default production configuration
 RUN mv "$PHP_INI_DIR/php.ini-production" "$PHP_INI_DIR/php.ini"
 
 # supervisord dependencies
-RUN set -ex; \
+RUN apt-get update && \
-    \
+    apt-get full-upgrade -y && \
-    apt-get update; \
+    apt-get install -y --no-install-recommends supervisor && \
-    apt-get install -y --no-install-recommends \
-        supervisor \
-    ; \
     rm -rf /var/lib/apt/lists/*
 
 COPY supervisord.conf /etc/supervisord.conf