Samples use EOL'd TargetFrameworks

[mschofie]

Many samples use the "net6.0" TargetFramework moniker, but - as per the .Net and .Net Core Official Support Policy - .net6.0 fell out of support on November 12, 2024. If I attempt to build those samples with a supported dotnet sdk, I get build errors:

"S:\source\github\microsoft\WindowsAppSDK-Samples\samples\Input\cs-winui\Input.sln" (default target) (1) ->
"S:\source\github\microsoft\WindowsAppSDK-Samples\samples\Input\cs-winui\Input.csproj" (default target) (2) ->
(_CheckForEolTargetFrameworks target) ->
  C:\Program Files\dotnet\sdk\9.0.305\Sdks\Microsoft.NET.Sdk\targets\Microsoft.NET.EolTargetFrameworks.targets(32,5): e
rror NETSDK1138: The target framework 'net6.0-windows10.0.19041.0' is out of support and will not receive security upda
tes in the future. Please refer to https://aka.ms/dotnet-core-support for more information about the support policy. [S
:\source\github\microsoft\WindowsAppSDK-Samples\samples\Input\cs-winui\Input.csproj]

Moving to net8.0 (which is the latest LTS release) doesn't seem unreasonable..?