Fix spelling of etc. in messages per Translatewiki request

Summary: Closes T15839

Test Plan: Read the code and see that it is spelled correctly

Reviewers: O1 Blessed Committers, avivey

Reviewed By: O1 Blessed Committers, avivey

Subscribers: avivey, tobiaswiese, valerio.bozzolan, Matthew, Cigaryno

Maniphest Tasks: T15839

Differential Revision: https://we.phorge.it/D25670