Use correct focus overlay for raised buttons

- Only uses themed overlay for flat buttons and flat icon buttons
- Dark overlay applies to all other buttons
- Fixes #3820

Author: willshowell

src/lib/button/_button-theme.scss

@@ -74,14 +74,8 @@
   $background: map-get($theme, background);
   $foreground: map-get($theme, foreground);
 
-  .mat-button, .mat-icon-button, .mat-raised-button, .mat-fab, .mat-mini-fab {
-    // Appy color to focus overlay.
-    // The focus overlay will be visible when any button type is focused or when
-    // flat buttons or icon buttons are hovered.
-    @include _mat-button-focus-color($theme);
-  }
-
   .mat-button, .mat-icon-button {
+    @include _mat-button-focus-color($theme);
     @include _mat-button-theme-color($theme, 'color');
     background: transparent;
   }