Remove editor back button height override (#52835)

In newer Gutenberg versions, this causes about a pixel
of whitespace above the button, which is very glaring.
Removing the override results in a clean UI in both prod
and edge.

apps/editing-toolkit/editing-toolkit-plugin/wpcom-block-editor-nav-sidebar/src/components/toggle-sidebar-button/style.scss

@@ -3,15 +3,12 @@
 @import '../nav-sidebar/style.scss';
 
 .wpcom-block-editor-nav-sidebar-toggle-sidebar-button__button {
-	height: $header-height !important;
-
 	// Match this animation with the nav-sidebar, so that the button is not hidden
 	// before the sidebar menu finishes sliding out.
 	transition: visibility $sidebar-transition-period linear;
 	@include reduce-motion( 'transition' );
 
 	&.is-hidden {
 		visibility: hidden;
-
 	}
 }