fix deprecation warning

Author: dpo

styles/decoration.atom-text-editor.less

@@ -3,7 +3,7 @@
 @green-color: @syntax-color-added;
 @blue-color: @syntax-color-renamed;
 
-atom-text-editor::shadow .gutter .line-number {
+atom-text-editor.editor .gutter .line-number {
   &.line-number-green {
     color: #fff;
     background-color: @green-color;