fix: move "email address changed by admin" notification setting to User Management chapter

[joshtrichards]

☑️ Resolves

This is an app setting and it was also hard-coded at the end of the config.php parameters reference chapter (note: did not come from the config sample in server). This PR moves it to it's relevant chapter and drops it from the config.php parameters chapter.

Also made some (minimal) fixes to typos, grammar, etc in the User Management chapter.

🖼️ Screenshots

AFTER

BEFORE