test: Fix fallout in tests

src/test/compile-fail/object-does-not-impl-trait.rs

@@ -11,9 +11,7 @@
 // Test that an object type `Box<Foo>` is not considered to implement the
 // trait `Foo`. Issue #5087.
 
-use std::marker::MarkerTrait;
-
-trait Foo : MarkerTrait {}
+trait Foo {}
 fn take_foo<F:Foo>(f: F) {}
 fn take_object(f: Box<Foo>) { take_foo(f); }
 //~^ ERROR the trait `Foo` is not implemented