[trimming] remove $(NullabilityInfoContextSupport) (#9069)

Context: dotnet/runtime#103970
Context: #9062 (comment)

This setting was removed in dotnet/runtime#103970, so
it doesn't do anything.

Author: jonathanpeppers

src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.DefaultProperties.targets

@@ -116,7 +116,6 @@
     <StartupHookSupport Condition="'$(StartupHookSupport)' == ''">false</StartupHookSupport>
     <UseNativeHttpHandler Condition=" $(AndroidHttpClientHandlerType.Contains ('System.Net.Http.SocketsHttpHandler')) And '$(UseNativeHttpHandler)' == '' ">false</UseNativeHttpHandler>
     <UseNativeHttpHandler Condition="'$(UseNativeHttpHandler)' == ''">true</UseNativeHttpHandler>
-    <NullabilityInfoContextSupport Condition="'$(NullabilityInfoContextSupport)' == ''">false</NullabilityInfoContextSupport>
     <BuiltInComInteropSupport Condition="'$(BuiltInComInteropSupport)' == ''">false</BuiltInComInteropSupport>
     <JsonSerializerIsReflectionEnabledByDefault Condition="'$(JsonSerializerIsReflectionEnabledByDefault)' == '' and '$(TrimMode)' == 'partial'">true</JsonSerializerIsReflectionEnabledByDefault>
     <MetricsSupport Condition="'$(MetricsSupport)' == ''">false</MetricsSupport>