Merge pull request matplotlib#25553 from greglucas/macosx-timer-main-thread

FIX: macosx, always put timers on main thread

Author: tacaswell

src/_macosx.m

@@ -1869,7 +1869,7 @@ static void context_cleanup(const void* info)
     CFTimeInterval interval;
     PyObject* py_interval = NULL, * py_single = NULL, * py_on_timer = NULL;
     int single;
-    runloop = CFRunLoopGetCurrent();
+    runloop = CFRunLoopGetMain();
     if (!runloop) {
         PyErr_SetString(PyExc_RuntimeError, "Failed to obtain run loop");
         return NULL;