refactor(DarkMode.less): improve style

resources/ext.DarkMode.less

@@ -288,12 +288,6 @@
 			border-top: 0;
 		}
 
-		/* Gadgets */
-		.in-page-edit .CodeMirror {
-			background-color: #eaecf0 !important;
-			color: #000 !important;
-		}
-
 		#scrollDownButton,
 		#scrollUpButton {
 			-webkit-transition: unset;