Drop mediawiki.skinning.interface in preparation for its deprecation

Since MonoBook is never cached on Wikimedia wikis, we don't need
to do anything about both modules being loaded in cached HTML.
There should be no differences before and after this change.

The change must apply to skins.monobook.styles and skins.monobook.responsive
as these modules never load at the same time (see setupSkinUserCss).

Bug: T242177
Change-Id: I5e69cd7f37f7b7a2b6325177b6688a426d92d57f

includes/SkinMonoBook.php

@@ -61,7 +61,6 @@ class SkinMonoBook extends SkinTemplate {
 		}
 
 		$out->addModuleStyles( [
-			'mediawiki.skinning.interface',
 			'mediawiki.skinning.content.externallinks',
 			$styleModule
 		] );

skin.json

@@ -33,6 +33,8 @@
 	},
 	"ResourceModules": {
 		"skins.monobook.styles": {
+			"class": "ResourceLoaderSkinModule",
+			"features": [ "elements", "content", "interface", "logo" ],
 			"styles": {
 				"resources/screen-common.less": {
 					"media": "screen"
@@ -43,6 +45,8 @@
 			}
 		},
 		"skins.monobook.responsive": {
+			"class": "ResourceLoaderSkinModule",
+			"features": [ "elements", "content", "interface", "logo" ],
 			"targets": [ "desktop", "mobile" ],
 			"styles": {
 				"resources/screen-common.less": {