Makes Plugin Settings gear adjust to dark mode.

It wasn't visible in dark mode before because it was
black on black. This makes it adjust automatically.

Change-Id: I5176cffc01842509ddafc4f30ff5029a0c4b8050
diff --git a/res/layout/switch_preference_with_settings.xml b/res/layout/switch_preference_with_settings.xml
index d319561..cd51833 100644
--- a/res/layout/switch_preference_with_settings.xml
+++ b/res/layout/switch_preference_with_settings.xml
@@ -26,7 +26,7 @@
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:src="@drawable/ic_setting"
-        android:tint="@android:color/black"
+        android:forceDarkAllowed="true"
         android:padding="12dp"
         android:background="?android:attr/selectableItemBackgroundBorderless" />