Fix translation of visibility levels

The following discussion from !53443 (merged) should be addressed:

• @manojmj started a discussion:

  Note to maintainer: This line been changed from current implementation because the existing implementation (ie, Project.visibility_levels.key(project.visibility_level_value).downcase) outputs the value like 'visibilitylevel|internal', while the value should just be internal.

  This fix is similar to the fix that has already been done for Project hook data in 7dbf114f.

  We should also fix the incorrect translation process over here that is the root cause for the incorrect translation in the current implementation. The fix is to use s_() instead of N_() for translation. This can be a follow-up issue.