gnome-shell: Fix looking glass buttons styling

The looking glass dialog is dark on lighter variant, so %osd_button
should be used instead of regular %button.

common/gnome-shell/44/sass/_common.scss

@@ -2813,7 +2813,7 @@ $_dash_bottom_margin: 20px;
     .lg-toolbar-button {
       padding: 5px 10px;
       border-radius: 2px;
-      @extend %button;
+      @extend %osd_button;
 
       & > StIcon { icon-size: 16px; }
     }
@@ -2824,21 +2824,12 @@ $_dash_bottom_margin: 20px;
     -natural-hpadding: 12px;
     -minimum-hpadding: 6px;
     font-weight: bold;
-    color: $osd_fg_color;
-    transition-duration: 100ms;
     padding-left: .3em;
     padding-right: .3em;
     border-radius: 2px;
+    @extend %osd_button;
 
-    &:hover {
-      color: $_panel_fg_color;
-      background-color: transparentize($_panel_fg_color, 0.95);
-    }
-    &:selected {
-      border-bottom-width: 0px;
-      color: $selected_fg_color;
-      background-color: $selected_bg_color;
-    }
+    &:selected { @include button(osd-active); }
   }
   StBoxLayout#EvalBox { padding: 4px; spacing: 4px; }
   StBoxLayout#ResultsArea { spacing: 4px; }