Demo: target .NET 6

Author: swharden

src/Spectrogram.MicrophoneDemo/Spectrogram.Demo.csproj

@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFramework>net5.0-windows</TargetFramework>
+    <TargetFramework>net6.0-windows</TargetFramework>
     <OutputType>WinExe</OutputType>
     <GenerateAssemblyInfo>false</GenerateAssemblyInfo>
     <UseWindowsForms>true</UseWindowsForms>