enh(settings): Set main page heading

[Pytal]

• For [BITV] 9.1.3.1a/9.1 - The page lacks an "h1" heading, and the existing "h2" heading, "Groups," does not accurately describe the content of the page and therefore cannot serve as the main heading for the page. (1) #41829

Summary

• Set main page heading for User management and Apps pages based on the selected section

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)

[Pytal]

/backport bf3a8d1,32fad8f692b,29867d64c80 to stable28

[AndyScherzinger]

@Pytal manual backport needed, afaik the bot can only to PR or commit, but not a set of explicitly mentioned commits

[AndyScherzinger]

nevermind, seems the bot was able to do it ?! 👀