Replace hard-coded strings for env.t on views/shared/modals folder

@paglias I didn't commit drops.jade and though I've replaced strings in it, I used the version from #2482, so I'm waiting for feedback to see if it's going to be merged or dropped. And I didn't touch the file newstuff.jade as there was no decision on what to do with it.

Forgot to add that login.jade wasn't touched as there is a comment on it that states it's no longer being used.

This PR goes along with [habitrpg-shared #110](https://github.com/HabitRPG/habitrpg-shared/pull/110)