Administration: Remove a blank space in the Recent Comments dashboard widget...

Administration: Remove a blank space in the Recent Comments dashboard widget if avatars are disabled on Discussion Settings screen.

Props Marius84, shital-patel, GaryJ, ianbelanger, sgastard, lgrev01, donmhico, garrett-eclipse, audrasjb, SergeyBiryukov.
Fixes #42938.
Built from https://develop.svn.wordpress.org/trunk@47255


git-svn-id: https://core.svn.wordpress.org/trunk@47055 1a063a9b-81f0-0310-95a4-ce76da25c4cd