Enhancement: Branding option to disable warning for multiple sync_journal.db's

We added a branding option that disables the `Multiple accounts are sharing the folder` warning.
In previous client versions a bug caused the creation of new sync journals, causing false positives in the detection.
While this can be handled by the individual user, companies with multiple hundreds of users may opt to disable the warning.

https://github.com/owncloud/client/pull/9216
