Fix FormValidation check when overwriting scopes when using the OicServerWellKnownConfiguration

[eva-mueller-coremedia]

The field name in config.jelly for OicServerWellKnownConfiguration is scopesOverride not overrideScopes.
This PR aligns the Java method.

Testing done

This change has been tested by unit tests as well as manual local testing with mvn clean hpi:run.

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 72.04%. Comparing base (41f98d9) to head (d6a5398).
Report is 11 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #507      +/-   ##
============================================
+ Coverage     71.73%   72.04%   +0.30%     
- Complexity      222      235      +13     
============================================
  Files            17       18       +1     
  Lines          1033     1073      +40     
  Branches        148      149       +1     
============================================
+ Hits            741      773      +32     
- Misses          201      207       +6     
- Partials         91       93       +2     

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