Docs: Improve description for the JS function that hides the update button for...

Docs: Improve description for the JS function that hides the update button for expired plugin or theme uploads.

Add missing `@since` tag.

Follow-up to [48417].

See #50612.
Built from https://develop.svn.wordpress.org/trunk@48427


git-svn-id: https://core.svn.wordpress.org/trunk@48196 1a063a9b-81f0-0310-95a4-ce76da25c4cd