This error occurs if `nextcloud-occ maintenance:install` fails and the
`upgrade` command is attempted to be executed afterwards.
Due to the nature of the installer we can't do much about it, so I guess
it makes sense to add some notes about it. The other notes in the
`Pitfalls`-section are semantically a list of different topics, so I
changed that accordingly now.
Closes#111175
(cherry picked from commit 561418f996fc015f4db48b1c9b7c31338cb280d9)
c19b0bf9de