Post Thumbnails: Fix squashed featured image in wp-admin.

This updates the CSS for featured images in the classic editor that caused images to look skewed when auto-sizes are enabled.

Props maciejmackowiak, sainathpoojary, mukesh27, joemcgill.
Fixes #62597.


git-svn-id: https://develop.svn.wordpress.org/trunk@59773 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/css/edit.css

@@ -308,7 +308,6 @@ ul.wp-tab-bar li {
 #postimagediv .inside img {
 	max-width: 100%;
 	height: auto;
-	width: auto;
 	vertical-align: top;
 	background-image: linear-gradient(45deg, #c3c4c7 25%, transparent 25%, transparent 75%, #c3c4c7 75%, #c3c4c7), linear-gradient(45deg, #c3c4c7 25%, transparent 25%, transparent 75%, #c3c4c7 75%, #c3c4c7);
 	background-position: 0 0, 10px 10px;