Add Tournament Committee user group and pluralise the User_groups page

[Albionthegreat]

Updates and renames the User_groups page to include the Tournament Committee.

All plurals in translations I wasn't sure about were done with the help of people who natively speak those languages. Thank you!

• bibitaru
• Kobold84
• Maxus
• Sies
• Sylphi

[osu-wiki-observatory]

Someone else has edited same files as you did. Please check their changes in case they conflict with yours:

• [EN] Update NAT, Alumni, osu!team members #12731, files:
  • wiki/People/Nomination_Assessment_Team/en.md

[osu-wiki-observatory]

Someone else has edited same files as you did. Please check their changes in case they conflict with yours:

• [DE] Update Main page #12779, files:
  • wiki/Main_page/de.md

[osu-wiki-observatory]

Someone else has edited same files as you did. Please check their changes in case they conflict with yours:

• Add missing word to Global Moderation Team #12796, files:
  • wiki/People/Global_Moderation_Team/en.md

[osu-wiki-observatory]

Someone else has edited same files as you did. Please check their changes in case they conflict with yours:

• Add Tournament Committee to User group list #12799, files:
  • wiki/People/User_group/en.md