These are HTTPSEverywhere rules that force a bunch of sites to be loaded under their .onion HS equivalent, for the request actually leaves the browser.
Idea taken from Forcing .onion on Whonix.org
See also Alec Muffett's list of .onion sites that don't suck
A reminder to myself that these go here on a Whonix workstation:
~/.tb/tor-browser/Browser/TorBrowser/Data/Browser/profile.default/HTTPSEverywhereUserRules