wait.2: Remove sys/types.h from the list of required headers

wait.h is self-contained.

MFC after:	1 week
Sponsored by:	The FreeBSD Foundation

lib/libc/sys/wait.2

@@ -28,7 +28,7 @@
 .\"     @(#)wait.2	8.2 (Berkeley) 4/19/94
 .\" $FreeBSD$
 .\"
-.Dd August 11, 2019
+.Dd June 24, 2022
 .Dt WAIT 2
 .Os
 .Sh NAME
@@ -42,7 +42,6 @@
 .Sh LIBRARY
 .Lb libc
 .Sh SYNOPSIS
-.In sys/types.h
 .In sys/wait.h
 .Ft pid_t
 .Fn wait "int *status"