fix(ui): toolbars background color

Author: Guillaume Chau

packages/@vue/cli-ui/src/components/FileDiffView.vue

@@ -238,7 +238,7 @@ export default {
 
   .toolbar
     padding $padding-item
-    background $color-background-light
+    background $md-white
     h-box()
     align-items center
 

packages/@vue/cli-ui/src/components/FolderExplorer.vue

@@ -225,7 +225,7 @@ export default {
 
 .toolbar
   padding $padding-item
-  background $color-background-light
+  background $md-white
   h-box()
   align-items center