Rename trait_of_item -> trait_of_assoc

compiler/rustc_monomorphize/src/partitioning.rs

@@ -650,7 +650,7 @@ fn characteristic_def_id_of_mono_item<'tcx>(
             // its self-type. If the self-type does not provide a characteristic
             // DefId, we use the location of the impl after all.
 
-            if tcx.trait_of_item(def_id).is_some() {
+            if tcx.trait_of_assoc(def_id).is_some() {
                 let self_ty = instance.args.type_at(0);
                 // This is a default implementation of a trait method.
                 return characteristic_def_id_of_type(self_ty).or(Some(def_id));