Workaround flaky SSL connection installing Android SDKs

[jamescrosswell]

In our GitHub Actions we're trying to install the android sdks by running:

dotnet build src/Sentry/Sentry.csproj -t:InstallAndroidDependencies -f:net8.0-android34.0 -p:AcceptAndroidSDKLicenses=True -p:AndroidSdkPath="/usr/local/lib/android/sdk/"

This command often fails to download the necessary dependencies due to SSL certificate errors:

/Users/runner/.dotnet/packs/Microsoft.Android.Sdk.Darwin/34.0.145/tools/Xamarin.Installer.Common.targets(12,3): 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/src/Sentry/Sentry.csproj::TargetFramework=net8.0-android34.0]

When this happens, we have to manually rerun the job, which is painful.

This PR simply retries that command once, if it fails the first time... so some basic resilience.

#skip-changelog