fix: update description to mention that data model binding and label are required

[JamalAlabdullah]

Description

• Updated the description for the column of Tabell for underskjema in subform.

Related Issue(s)

• Update description to mention that data model binding and label are required #14260

Verification

• Your code builds clean without any errors or warnings
• Manual testing done (required)
• Relevant automated test added (if you find this hard, leave it and we'll help out)

Documentation

• User documentation is updated with a separate linked PR in altinn-studio-docs. (if applicable)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.52%. Comparing base (2345ba1) to head (adbe7e5).

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #14281   +/-   ##
=======================================
  Coverage   95.52%   95.52%           
=======================================
  Files        1829     1829           
  Lines       23775    23775           
  Branches     2754     2754           
=======================================
  Hits        22710    22710           
  Misses        807      807           
  Partials      258      258           

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