[Tails-dev] Small fix in documentation

Hello, I fix three pages in this branch:

Repo : https://git-tails.immerda.ch/xin/tails/
Branch : smallfix
Last Commit : 34e0503fabae36e3349a9256fc8c0353c5a72c21

In wiki/src/install/mac/usb/overview.html I fix a typo, in
wiki/src/doc/anonymous_internet/Tor_Browser.mdwn I add a more usefull
alt for an image and in wiki/src/doc/about/warning.mdwn
b/wiki/src/doc/about/warning.mdwn I update the links.

Cheers.
xin