Remove BitmapSelector.Suffix property (#54364)

Remove BitmapSelector.Suffix property (#54364)

With https://github.com/dotnet/runtime/issues/22761 and https://github.com/dotnet/corefx/pull/22833, BitmapSelector.Suffix will always be null. This means this feature is dead code, and users are unable to use it.

Removing this dead code because:

1. It doesn't do anything.
2. It is causing ILLink warnings, and it is easier to delete than to try to address the warnings.

I logged https://github.com/dotnet/runtime/issues/54363 to follow up and either re-implement this feature, or obsolete the attributes that no longer have any effect on the app.