[stable8] fix(NcFormGroup): remove margin when no label/description

[backportbot]

Backport of #7764

Warning, This backport's changes differ from the original and might be incomplete ⚠️

Todo

• Review and resolve any conflicts
• Amend HEAD commit to remove the line stating to skip CI

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Learn more about backports at https://docs.nextcloud.com/server/stable/go.php?to=developer-backports.

[codecov]

Codecov Report

❌ Patch coverage is 55.55556% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 44.88%. Comparing base (68e8736) to head (cfcbb23).
⚠️ Report is 2 commits behind head on stable8.

Files with missing lines	Patch %	Lines
src/components/NcFormGroup/NcFormGroup.vue	55.55%	4 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##           stable8    #7780   +/-   ##
========================================
  Coverage    44.88%   44.88%           
========================================
  Files          180      180           
  Lines         4465     4465           
  Branches      1168     1169    +1     
========================================
  Hits          2004     2004           
  Misses        2366     2366           
  Partials        95       95           

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