packaging: remove obsolete config file in d/preinst

debian/preinst

@@ -12,6 +12,10 @@ case "$1" in
             rm -f /etc/dconf/db/gdm.d/02-logo
             rm -f /etc/dconf/db/gdm.d/03-smartcard
         fi
+        # in version > 0.6, proxy config was moved to another package
+        if dpkg --compare-versions "$2" le 0.6 ; then
+            rm -f /etc/dconf/db/local.d/01-proxy
+        fi
         ;;
     abort-upgrade)
         ;;