Update comment in posixmodule.c (GH-5681)

A closing parentheses was missing.

Signed-off-by: Ngie Cooper <[email protected]>
(cherry picked from commit 7745ec4)

Co-authored-by: ngie-eign <[email protected]>

Author: miss-islington

Modules/posixmodule.c

@@ -3936,7 +3936,7 @@ posix_fork(PyObject *self, PyObject *noargs)
 #ifdef HAVE_STROPTS_H
 #include <stropts.h>
 #endif
-#endif /* defined(HAVE_OPENPTY) || defined(HAVE_FORKPTY) || defined(HAVE_DEV_PTMX */
+#endif /* defined(HAVE_OPENPTY) || defined(HAVE_FORKPTY) || defined(HAVE_DEV_PTMX) */
 
 #if defined(HAVE_OPENPTY) || defined(HAVE__GETPTY) || defined(HAVE_DEV_PTMX)
 PyDoc_STRVAR(posix_openpty__doc__,