fn-trait-closure test now pass on new solver

Author: spastorino

tests/ui/traits/new-solver/fn-trait-closure.rs

@@ -1,12 +1,5 @@
 // compile-flags: -Ztrait-solver=next
-// known-bug: unknown
-// failure-status: 101
-// dont-check-compiler-stderr
-
-// This test will fail until we fix `FulfillmentCtxt::relationships`. That's
-// because we create a type variable for closure upvar types, which is not
-// constrained until after we try to do fallback on diverging type variables.
-// Thus, we will call that function, which is unimplemented.
+// check-pass
 
 fn require_fn(_: impl Fn() -> i32) {}