[python] Remove explicit visibility("default") on PyInit__message (#1…

…6125)

This is unnecessary as PyMODINIT_FUNC already implies Py_EXPORTED_SYMBOL.

Closes #16125

COPYBARA_INTEGRATE_REVIEW=#16125 from goffrie:upb_export 5e7fa70
PiperOrigin-RevId: 700793109

python/protobuf.c

@@ -401,7 +401,7 @@ bool PyUpb_IndexToRange(PyObject* index, Py_ssize_t size, Py_ssize_t* i,
 // Module Entry Point
 // -----------------------------------------------------------------------------
 
-__attribute__((visibility("default"))) PyMODINIT_FUNC PyInit__message(void) {
+PyMODINIT_FUNC PyInit__message(void) {
   PyObject* m = PyModule_Create(&module_def);
   if (!m) return NULL;