change an todo comment in a scss file

src/client/styles/scss/_on-edit.scss

@@ -316,7 +316,7 @@ body.on-edit {
   height: 135px;
 }
 
-// [TODO support dark mode by GW-3037]
+// [border-colors:TODO support dark mode by GW-3037]
 .grid-bg-col,
 .grid-editable-col {
   border-right: 5px solid white;