Administration: Remove `wp-auth-check` from the Heartbeat API.

As of [27153], wp-auth-check is returned on all heartbeats without the need for data from client-side. This also means that the timing and scheduling of this request data is ineffectual.

Fixes #50305.

Props dsixinetu, azaozz, whyisjake.


Built from https://develop.svn.wordpress.org/trunk@48056


git-svn-id: https://core.svn.wordpress.org/trunk@47823 1a063a9b-81f0-0310-95a4-ce76da25c4cd