Switch Check's TODO to use SemIRLocation (#3779)

Allows dropping a few GetNodeId calls for code cleanliness.

toolchain/check/impl.cpp

@@ -104,7 +104,7 @@ static auto BuildInterfaceWitness(
       }
     } else if (auto const_decl = decl.TryAs<SemIR::AssociatedConstantDecl>()) {
       // TODO: Check we have a value for this constant in the constraint.
-      context.TODO(context.insts().GetNodeId(impl.definition_id),
+      context.TODO(impl.definition_id,
                    "impl of interface with associated constant");
       return SemIR::InstId::BuiltinError;
     } else {
@@ -127,8 +127,7 @@ auto BuildImplWitness(Context& context, SemIR::ImplId impl_id)
   auto interface_type =
       context.types().TryGetAs<SemIR::InterfaceType>(impl.constraint_id);
   if (!interface_type) {
-    context.TODO(context.insts().GetNodeId(impl.definition_id),
-                 "impl as non-interface");
+    context.TODO(impl.definition_id, "impl as non-interface");
     return SemIR::InstId::BuiltinError;
   }