Update LangVersion to 9.0

Author: amaitland

CefSharp.Wpf.HwndHost.Example/CefSharp.Wpf.HwndHost.Example.csproj

@@ -8,6 +8,7 @@
 		<StartupObject>CefSharp.Wpf.HwndHost.Example.App</StartupObject>
 		<PlatformTarget>AnyCPU</PlatformTarget>
 		<ApplicationManifest>app.manifest</ApplicationManifest>
+        <LangVersion>9.0</LangVersion>
 	</PropertyGroup>
 
     <PropertyGroup Condition="'$(TargetFramework)' == 'netcoreapp3.1'">

CefSharp.Wpf.HwndHost/CefSharp.Wpf.HwndHost.csproj

@@ -20,6 +20,7 @@
         <CefSharpBuildAction>NoAction</CefSharpBuildAction>
         <SignAssembly>true</SignAssembly>
         <AssemblyOriginatorKeyFile>..\CefSharp.snk</AssemblyOriginatorKeyFile>
+        <LangVersion>9.0</LangVersion>
     </PropertyGroup>
 
     <ItemGroup Condition="'$(TargetFramework)' == 'net462'">