[Regional Preferences] Remove u extension for subtitle of Language

 - Remove the language tag info of subtitle in  Settings -> System -> Languages
 - Syuc same result to entry of numbering system.

Bug: b/268278327
Bug: b/268276472
Test: atest passed
Test: Manual test passed
Change-Id: I46dd0899059e9209b99f5ef3b7b84eb083d4e140