fix: improve the text contrast ratio of the editor sidebar

GitOrigin-RevId: 01fb558f3c8b1cff611200b2b309a28c7823305b

services/web/frontend/stylesheets/app/editor/left-menu.less

@@ -23,7 +23,7 @@
     font-size: 1rem;
     margin: (@line-height-computed / 2) 0;
     padding-bottom: (@line-height-computed / 4);
-    color: @gray-light;
+    color: @neutral-70;
     border-bottom: 1px solid @gray-lighter;
   }