Fix comment referring to function name

Author: cmaloney

Modules/_io/textio.c

@@ -672,8 +672,8 @@ struct textio
     int ok; /* initialized? */
     int detached;
     Py_ssize_t chunk_size;
-    /* Use helpers _textiowrapper_buffer_* to access buffer; many
-       operations can set it to NULL (see gh-143008, gh-142594). */
+    /* Use helpers buffer_* to access buffer; many operations can set it to
+       NULL (see gh-143008, gh-142594). */
     PyObject *buffer;
     PyObject *encoding;
     PyObject *encoder;