Drop support for EOL TFMs

[jamescrosswell]

Resolves #3806:

• Drop EOL targets #3806

[vaind]

lgtm, the integration test needs an update though:

/Users/runner/.dotnet/packs/Microsoft.Android.Sdk.Darwin/34.0.145/tools/Xamarin.Installer.Common.targets(12,3): error : Failed to locate Android SDK at path `/Users/runner/Library/Android/sdk`. [/Users/runner/work/sentry-dotnet/sentry-dotnet/integration-test/maui-app/maui-app.csproj::TargetFramework=net8.0-android34.0]
    0 Warning(s)
    4 Error(s)

Time Elapsed 00:00:05.12

Describing MAUI
Error: [-] Describe MAUI failed
Message
  RuntimeException: Failed to install android dependencies.
  at <ScriptBlock>, /Users/runner/work/sentry-dotnet/sentry-dotnet/integration-test/cli.Tests.ps1:153

[vaind]

Suggested change

<!-- TODO check and update the list of supported frameworks. -->

[jamescrosswell]

Failed to install android dependencies

From what I can tell, this is an intermittent failure:

error : Failed to download Xamarin Repository manifest from https://aka.ms/AndroidManifestFeed/d17-12. System.AggregateException: One or more errors occurred. (The SSL connection could not be established, see inner exception.) [/Users/runner/work/sentry-dotnet/sentry-dotnet/integration-test/maui-app/maui-app.csproj::TargetFramework=net8.0-android34.0]

The aka.ms servers don't seem very reliable. On my Windows machine, I often have to run dotnet workload restore 3 to 4 times before it succeeds (regularly fails to validate the SSL certs).