Revert "Mentee overview: Truncate long usernames"

This reverts commit 6df9d7924d8715b0c13216a68d47fee0663097a2.

Reason for revert: on smaller screen, this truncates way too
early. Reverting, will work on a better patch later.

Bug: T292224
Change-Id: Ife311cca0dddf8662d204956db84436566afe269