maintenance command deprecation

[jremmurd]

In Pimcore 5.8 the ./bin/console maintenance command is no longer available.
There should either be

• a documentation that it is now no longer supported and has to be called under the pimcore: namespace (https://pimcore.com/docs/5.x/Development_Documentation/Installation_and_Upgrade/Upgrade_Notes/Within_V5/index.html#page_Version-5-8-0)

• or the alias should be activated again.

[dpfaffenbauer]

1. Note should be enough