Remove line ref to old icon

src/vs/workbench/browser/parts/editor/media/editorgroupview.css

@@ -89,15 +89,6 @@
 	background-repeat: no-repeat;
 }
 
-.vs .monaco-workbench .part.editor > .content .editor-group-container > .editor-group-container-toolbar .close-editor-group {
-	background-image: url('close-light.svg');
-}
-
-.vs-dark .monaco-workbench .part.editor > .content .editor-group-container > .editor-group-container-toolbar .close-editor-group,
-.hc-black .monaco-workbench .part.editor > .content .editor-group-container > .editor-group-container-toolbar .close-editor-group {
-	background-image: url('close-dark.svg');
-}
-
 /* Editor */
 
 .monaco-workbench .part.editor > .content .editor-group-container.empty > .editor-container  {