[illink] Do not preserve ConstructorBuilder

Part of dotnet#5167

The type is not accessed by reflection. It can also be made static,
but that is already part of dotnet#5360

Removed API from BuildReleaseArm64False test:

    Type Android.Runtime.ConstructorBuilder
      -             Method public SIGERR .ctor ()

src/Microsoft.Android.Sdk.ILLink/PreserveLists/Mono.Android.xml

@@ -4,7 +4,6 @@
 		<type fullname="Android.Runtime.AndroidEnvironment" />
 		<type fullname="Android.Runtime.AnnotationAttribute" />
 		<type fullname="Android.Runtime.CharSequence" />
-		<type fullname="Android.Runtime.ConstructorBuilder" />
 		<type fullname="Android.Runtime.Extensions" />
 		<type fullname="Android.Runtime.GeneratedDummyHost" />
 		<type fullname="Android.Runtime.GeneratedEnumAttribute" />