Sync mozconfig files used in tor-browser over to tor-browser-build for esr68
If we don't make sufficient progress on legacy/trac#23656 (moved) this time we should at least make sure all the mozconfig files we use for our official builds contain all the things they should contain (and only those) (the --enable-proxy-bypass-protection option is one of them; the MOZILLA_OFFICIAL changes as well)
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