Fixed English in a comment; trimmed trailing whitespace;

no code changes.

Objects/dictobject.c

@@ -519,10 +519,10 @@ PyDict_GetItem(PyObject *op, PyObject *key)
 }
 
 /* CAUTION: PyDict_SetItem() must guarantee that it won't resize the
- * dictionary if it is merely replacing the value for an existing key.
- * This is means that it's safe to loop over a dictionary with
- * PyDict_Next() and occasionally replace a value -- but you can't
- * insert new keys or remove them.
+ * dictionary if it's merely replacing the value for an existing key.
+ * This means that it's safe to loop over a dictionary with PyDict_Next()
+ * and occasionally replace a value -- but you can't insert new keys or
+ * remove them.
  */
 int
 PyDict_SetItem(register PyObject *op, PyObject *key, PyObject *value)