Enable Multiple GitHub Auth for Stable

[TylerLeonhardt]

Follow up from #127967 (comment)

[TylerLeonhardt]

With tomorrow's Insiders build (this PR), Multiple GitHub account will be enabled by default.

In order to log in to a second account you either need to:

• Start a log in flow to a new extension or feature (Settings Sync, Cloud Changes, Tunnels)
• Go to this quick pick and choose the new Use a new account... option (not pictured, but it'll be there) Multiple GitHub account support #127967 (comment)
• Change your account in Settings Sync: https://code.visualstudio.com/docs/editor/settings-sync#_switching-accounts