fix: modal size for lti content

[Faraz32123]

Ticket: COSMO2-716

• dialogClassName was working with Modal from paragon, but after paragon v23 upgrade. We replaced Modal with ModalDialog with which dialogClassName doesn't work.
  • So, replace dialogClassName with simple className to apply same styles to get the past behavior for the modal.

Please review
paragon v22 Modal Props VS paragon ModalDialog Props API which used className instead of dialogClassName.

Link to upstream openedx PR: openedx#1787

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
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⚠️ Report is 694 commits behind head on master.

Additional details and impacted files

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##             master      #12   +/-   ##
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  Coverage          ?   90.90%           
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  Files             ?      344           
  Lines             ?     5784           
  Branches          ?     1372           
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  Hits              ?     5258           
  Misses            ?      507           
  Partials          ?       19           

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