settings: Fix strings, copy and capitalization

Addresses the issues pointed out in:
https://gerrit.wikimedia.org/r/#/c/140086/16/i18n/en.json

Discussion:
https://trello.com/c/NYQ0nMeE/101-hovercards-phase-3

Bug: 68812
Change-Id: I7b4f6d2be08a1ee20b19aec95d99a73fd4bf9d29