upgrade to winUI 2.7

Author: TatianaKapos

example/windows/ExperimentalFeatures.props

@@ -23,7 +23,7 @@
       See https://microsoft.github.io/react-native-windows/docs/winui3
     -->
     <UseWinUI3>false</UseWinUI3>
-    <WinUI2xVersion>2.6.0</WinUI2xVersion>
+    <WinUI2xVersion>2.7.0</WinUI2xVersion>
 
     <!--
       Changes compilation to assume use of Microsoft.ReactNative NuGet packages

examplenuget/windows/ExperimentalFeatures.props

@@ -35,7 +35,7 @@
 
     <ReactExperimentalFeaturesSet>true</ReactExperimentalFeaturesSet>
     <ReactNativeWindowsVersion>0.71.0</ReactNativeWindowsVersion>
-    <WinUI2xVersion>2.6.0</WinUI2xVersion>
+    <WinUI2xVersion>2.7.0</WinUI2xVersion>
 
   </PropertyGroup>