[DOCS] Remove incorrect slash in extension paths

An incorrect slash has been removed in multiple extension
paths. The slash could lead to exceptions (e.g. within the
form framework's `PersistenceManagerException` configuration),
as those paths cannot be resolved,

Additionally, a proper role has been added to some of
those paths.

Releases: master, 9.5
Resolves: #89942
Change-Id: I70f5e67d5cc7f58e66507242158e565cd8c70720
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/62626


Tested-by: Björn Jacob <bjoern.jacob@tritum.de>
Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Daniel Goerz <daniel.goerz@posteo.de>
Reviewed-by: Björn Jacob <bjoern.jacob@tritum.de>
Reviewed-by: Daniel Goerz <daniel.goerz@posteo.de>