* Removed prereq.md, updated description in Overview topic.

* Fixed relref for manage users.

* Update docs/sources/panels/transformations/_index.md

Co-authored-by: Torkel Ödegaard <torkel@grafana.org>

* Removed extra "the"

* Changed "In case" to "If"

Co-authored-by: Torkel Ödegaard <torkel@grafana.org>