Fix gray tag selector background color on Linux/Windows

8337b7ec1 fixed a regression in the Reactified tag selector that
prevented it from using GTK theme background colors on Linux, but it
accidentally made the background gray by default. This restores the
default white background.

Fixes #1684

scss/components/_tag-selector.scss

@@ -28,6 +28,7 @@
 	display: flex;
 	overflow: hidden;
 	height: 100px;
+	background-color: $tag-selector-bg;
 }
 
 .tag-selector-list-container > div {

scss/mac/_tag-selector.scss

@@ -2,10 +2,6 @@
 // Tag selector
 // --------------------------------------------------
 
-.tag-selector-list-container {
-  background-color: $tag-selector-bg;
-}
-
 .tag-selector-filter-container {
   padding: 0.25em 0 0.25em 0.5em;
   border-top: 1px solid $shade-3;

scss/themes/_light.scss

@@ -173,4 +173,4 @@ $modal-footer-border-color:   $shade-2;
 $modal-icon-spin-color:       $shade-0;
 
 // Tag selector
-$tag-selector-bg:             $shade-0;
+$tag-selector-bg:             -moz-field;