Workbench: Cleanup the installed MariaDB packages.

The mariadb-client and default-mysql-client packages conflict and I have
no idea what the mariadb package contains (doesn't exist and can't find
which package provides it).

workbench/Dockerfile

@@ -25,7 +25,6 @@ RUN apt-get update && \
         curl \
         dbus-x11 \
         default-jdk-headless \
-        default-mysql-client \
         devscripts \
         direnv \
         dirmngr \
@@ -192,7 +191,6 @@ RUN apt-get update && \
         khard \
         litecli \
         magic-wormhole \
-        mariadb \
         mycli \
         netaddr \
         paramiko \