[dotnet] We no longer need to add the entry assembly as a root assemb…

…ly for the linker.

Not only is it no longer necessary (hasn't been for a while), it'll be wrong
in .NET 8 after dotnet/linker#3124.

dotnet/targets/Xamarin.Shared.Sdk.targets

@@ -574,9 +574,6 @@
  <TrimMode>copy</TrimMode> <!-- Don't use 'copyused', because that might still end up saving some assemblies, and if that's the platform assembly, it may break the partial static registrar -->
  </ResolvedFileToPublish>
 
- <!-- Mark our entry assembly as a root assembly. -->
- <TrimmerRootAssembly Include="@(ResolvedFileToPublish)" Condition="'%(ResolvedFileToPublish.Filename)' == '$(AssemblyName)' And '%(ResolvedFileToPublish.Extension)' == '.dll'" />
-
  <!--
  pre-mark custom steps
  -->