[BUGFIX] Respect sys_language enable fields

This patch adds a call to BackendUtility::BEenableFields()
in the getSystemLanguages() of the TranslationConfigurationProvider
so that hidden records will not be returned any more.

Releases: 6.3, 6.2
Resolves: #59947
Change-Id: I1c73de4621c7490273ce2966130e53add70b81cd