UserNameSuggester suggests names with trailing underscores

[techAPJ (Arpit Jalan)]

Trailing underscore in username is now allowed:

FIX: Allow trailing `_` because we used to.

However UserNameSuggester still suggests usernames with a sequence of 2 or more special chars (like arpit__jalan) which is not valid. I am working on a fix for that. Fixed:

FIX: UserNameSuggester should not suggest usernames with a sequence of 2 or more special chars