Update .NET 11 samples to Preview 7 - #775

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@v4, actions/setup-dotnet@v4. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

Unexpected input(s) 'include-prerelease', valid inputs are ['dotnet-version', 'dotnet-quality', 'global-json-file', 'source-url', 'owner', 'config-file', 'cache', 'cache-dependency-path']

Found no csproj for file 11.0/global.json

Found no csproj for file 11.0/README.md

Found no csproj for file 11.0/Directory.Build.props