pycore_interp.h: Fix comment about pytypedefs.h (python#93188)

pythonGH-31527 moved this typedef to `Include/pytypedefs.h`, so this comment
should point at the correct location

Author: itamaro

Include/internal/pycore_interp.h

@@ -73,7 +73,7 @@ struct atexit_state {
 /* PyInterpreterState holds the global state for one of the runtime's
    interpreters.  Typically the initial (main) interpreter is the only one.
 
-   The PyInterpreterState typedef is in Include/pystate.h.
+   The PyInterpreterState typedef is in Include/pytypedefs.h.
    */
 struct _is {