bpo-31285: Remove splitlines identifier from Python/_warnings.c (#3803)

(forgot to remove it in #3219)

Author: orenmn

Python/_warnings.c

@@ -859,7 +859,6 @@ warnings_warn_explicit(PyObject *self, PyObject *args, PyObject *kwds)
 
  if (module_globals) {
  _Py_IDENTIFIER(get_source);
- _Py_IDENTIFIER(splitlines);
  PyObject *tmp;
  PyObject *loader;
  PyObject *module_name;
@@ -870,8 +869,6 @@ warnings_warn_explicit(PyObject *self, PyObject *args, PyObject *kwds)
 
  if ((tmp = _PyUnicode_FromId(&PyId_get_source)) == NULL)
  return NULL;
- if ((tmp = _PyUnicode_FromId(&PyId_splitlines)) == NULL)
- return NULL;
 
  /* Check/get the requisite pieces needed for the loader. */
  loader = PyDict_GetItemString(module_globals, "__loader__");