Issue #2423577 by LewisNyman, joelpittet: Remove Seven's appearance-page.css

core/themes/seven/css/theme/appearance-page.css

-/**
- * Appearance page.
- */
-.system-themes-list__header {
-  font-weight: normal;
-  text-transform: uppercase;
-}

core/themes/seven/seven.libraries.yml

@@ -34,8 +34,6 @@ global-styling:
       css/components/views-ui.css: {}
     layout:
       css/layout/layout.css: {}
-    theme:
-      css/theme/appearance-page.css: {}
 
 node-form:
   version: VERSION