Twenty Fifteen & Twenty Sixteen: Remove extra space around post editor.

The editor uses the full height of its container, so the added margins cause the visual editor to break out of the container. This removes the top & bottom margins, and makes the left & right margins consistent with the meta box area.

Props antonlukin, paaljoachim, felipeelia.
Reviewed by ryelle, SergeyBiryukov.
Merges [50465] to the 5.7 branch.
Fixes #52646.
Built from https://develop.svn.wordpress.org/branches/5.7@50468


git-svn-id: http://core.svn.wordpress.org/branches/5.7@50079 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-content/themes/twentyfifteen/css/editor-style.css

@@ -28,7 +28,7 @@ body {
 	font-weight: 400;
 	font-size: 17px;
 	line-height: 1.6471;
-	margin: 20px 40px;
+	margin: auto 20px;
 	max-width: 660px;
 	vertical-align: baseline;
 }

wp-content/themes/twentysixteen/css/editor-style.css

@@ -28,7 +28,7 @@ body {
 	font-size: 16px;
 	font-weight: 400;
 	line-height: 1.75;
-	margin: 20px 40px;
+	margin: auto 20px;
 	max-width: 600px;
 	vertical-align: baseline;
 }

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.7-RC1-50467';
+$wp_version = '5.7-RC1-50468';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.