bpo-39585: Delete a pending comment in _warning.c (GH-18414)

diff --git a/Python/_warnings.c b/Python/_warnings.c
index 39f8033..834ceb1 100644
--- a/Python/_warnings.c
+++ b/Python/_warnings.c
@@ -491,8 +491,9 @@
     PyOS_snprintf(lineno_str, sizeof(lineno_str), ":%d: ", lineno);
 
     name = _PyObject_GetAttrId(category, &PyId___name__);
-    if (name == NULL)  /* XXX Can an object lack a '__name__' attribute? */
+    if (name == NULL) {
         goto error;
+    }
 
     f_stderr = _PySys_GetObjectId(&PyId_stderr);
     if (f_stderr == NULL) {