T13: remove back-compat ruleset

Author: sabernhardt

src/wp-content/themes/twentythirteen/css/editor-blocks.css

@@ -59,12 +59,6 @@ Description: Used to style blocks in the editor.
 	max-width: 604px;
 }
 
-.editor-post-title__block,
-.editor-default-block-appender,
-.editor-block-list__block {
-	max-width: 634px; /* Account for padding in older WordPress versions. */
-}
-
 .wp-block.alignwide,
 .wp-block.alignfull {
 	max-width: inherit;