feat: disable new ORA experience for leaderboards

[nsprenkle]

TL;DR - disables ORA experience when leaderboards are enabled (not currently supported).

Developer Checklist

• Reviewed the release process
• Translations and JS/SASS compiled
• Bumped version number in openassessment/__init__.py and package.json

Testing Instructions

1. Go to Studio
2. Create / edit an ORA
3. Set "Top Responses" to a non-zero value.
4. Verify that we use the legacy ORA experience.

Reviewer Checklist

Collectively, these should be completed by reviewers of this PR:

• I've done a visual code review
• I've tested the new functionality

FYI: @openedx/content-aurora

[mattcarter]

approved

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (d88d1a7) 94.94% compared to head (8d02423) 94.94%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2140   +/-   ##
=======================================
  Coverage   94.94%   94.94%           
=======================================
  Files         191      191           
  Lines       20515    20524    +9     
  Branches     1858     1859    +1     
=======================================
+ Hits        19478    19487    +9     
  Misses        777      777           
  Partials      260      260           

Flag	Coverage Δ
unittests	94.94% <100.00%> (+<0.01%)	⬆️

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