Update VS templates for UWP unit testing to more power friendly default mode (#420)

Author: jayaranigarg

Templates/CSharp/UWP/ProjectTemplates/CSharp/Windows UAP/UnitTestApp.xaml

@@ -2,7 +2,6 @@
     x:Class="$safeprojectname$.App"
     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
-    xmlns:local="using:$safeprojectname$"
-    RequestedTheme="Light">
+    xmlns:local="using:$safeprojectname$">
 
 </Application>

Templates/VisualBasic/UWP/ProjectTemplates/VisualBasic/Windows UAP/UnitTestApp.xaml

@@ -2,7 +2,6 @@
     x:Class="$safeprojectname$.App"
     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
-    xmlns:local="using:$safeprojectname$"
-    RequestedTheme="Light">
+    xmlns:local="using:$safeprojectname$">
 
 </Application>