NO BUG - Remove unused string

This string is not used anywhere and it is also a typo
I have to update in transifex so that translators don't question about them
and they don't have to translate something that we don't ever use.
NOBUG - Fix link in /teach for WebLit

The link was reverted after @daleee's changes and this should be the final version
https://github.com/mozilla/webmaker.org/commit/b3821d9ebb52f223a6043e262e8c3c4543db94e5