editor: remove gutter background override

This was carried over from the Ace editor, but doesn't work well with
the Monaco editor.

Fixes: https://github.com/pybricks/pybricks-code/issues/472

CHANGELOG.md

@@ -6,6 +6,7 @@
 
 ### Changed
 - Changed snippet (autocomplete) content and behavior [issue#471].
+- Changed gutter background color [issue#472].
 
 ### Fixed
 - Fixed auto-indent not working [issue#470].
@@ -43,6 +44,7 @@ Prerelease changes are documented at [support#48].
 <!-- let's try to keep this list sorted -->
 [issue#470]: https://github.com/pybricks/pybricks-code/issues/470
 [issue#471]: https://github.com/pybricks/pybricks-code/issues/471
+[issue#472]: https://github.com/pybricks/pybricks-code/issues/472
 [support#48]: https://github.com/pybricks/support/issues/48
 [support#378]: https://github.com/pybricks/support/issues/378
 [v3.0.0]: https://github.com/pybricks/pybricks-micropython/blob/master/CHANGELOG.md#300---2021-06-08

src/editor/editor.scss

@@ -5,16 +5,6 @@
 
 @import '../variables.scss';
 
-// make editor match app backgound color
-
-.#{$ns}-dark .margin-view-overlays {
-    background-color: $pt-dark-app-background-color;
-}
-
-.margin-view-overlays {
-    background-color: $pt-app-background-color;
-}
-
 // add "BETA" watermark
 
 .pb-beta .editor-scrollable::after {