Administration: Better align labels on the discussion options page.

The labels for Comment Moderation, and Comment Blocklist are now aligned properly with the adjacent text.

Fixes #37384.
Props ankit-k-gupta, karmatosed, FolioVision, desrosj, valentinbora, samful, whyisjake.

Built from https://develop.svn.wordpress.org/trunk@48419


git-svn-id: https://core.svn.wordpress.org/trunk@48188 1a063a9b-81f0-0310-95a4-ce76da25c4cd