fix: Use the correct letter case for "ar-ARB" locale code

[hectoras]

Associated Jira issue: AUT-3264

Renames the directory for the Standard Arabic locale and updates the ISO code encoded in the files it contains so that the letter case matches the one used by other languages (that is lowercase-UPPERCASE).

This is needed in order for TAO to encode the language code for Standard Arabic with the proper case (ar-ARB) when setting the language on a Shared Stimulus to Arabic.

Note a quick check shows we may need also some migration to update the language code: Stimulus are still saved with the language set as "ar-arb" after switching to this branch and running taoUpdate

[github-actions]

Version

Target Version	53.6.2
Last version	53.6.1

There are 0 BREAKING CHANGE, 0 feature, 1 fix

[codecov-commenter]

Codecov Report

Patch and project coverage have no change.

Comparison is base (f91ee40) 27.58% compared to head (63d1a4c) 27.58%.
Report is 1 commits behind head on develop.

Additional details and impacted files

@@            Coverage Diff             @@
##             develop    #3879   +/-   ##
==========================================
  Coverage      27.58%   27.58%           
  Complexity     10978    10978           
==========================================
  Files            922      922           
  Lines          33919    33919           
==========================================
  Hits            9355     9355           
  Misses         24564    24564           

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