mysql-client is already part of base image

Dockerfile

@@ -1,7 +1,7 @@
 FROM cloudron/base:0.3.2
 
 RUN apt-get update && \
-    apt-get install -y openssh-server mysql-client && \
+    apt-get install -y openssh-server && \
     rm -r /var/cache/apt /var/lib/apt/lists
 
 ADD supervisor/ /etc/supervisor/conf.d/