Fix broken submission form row styling

[robinmolen]

Closes #4711

Changes

Changed the .form-row styling to be more specific.

Checklist

Check off the items that are completed or not relevant.

• Impact on features

  • Checked copying a form
  • Checked import/export of a form
  • Config checks in the configuration overview admin page
  • Problem detection in the admin email digest is handled

• Release management

  • I have labelled the PR as "needs-backport" accordingly

• I have updated the translations assets (you do NOT need to provide translations)

  • Ran ./bin/makemessages_js.sh
  • Ran ./bin/compilemessages_js.sh

• Commit hygiene

  • Commit messages refer to the relevant Github issue
  • Commit messages explain the "why" of change, not the how

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.56%. Comparing base (7b20acc) to head (531bb8b).
Report is 2 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #4715   +/-   ##
=======================================
  Coverage   96.56%   96.56%           
=======================================
  Files         746      746           
  Lines       25174    25174           
  Branches     3310     3310           
=======================================
  Hits        24309    24309           
  Misses        601      601           
  Partials      264      264           

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[sergei-maertens]

Backports:

• stable/2.8.x: d28023c
• stable/2.7.x: 77f6422
• stable/2.6.x: cb3dd7b