Site Health: Simplify the logic for displaying whether auto-updates are...

Site Health: Simplify the logic for displaying whether auto-updates are enabled for plugins and themes.

Remove some extra variables.

Follow-up to [48546], [48549].

See #50663.
Built from https://develop.svn.wordpress.org/trunk@48552


git-svn-id: https://core.svn.wordpress.org/trunk@48314 1a063a9b-81f0-0310-95a4-ce76da25c4cd