atomic.9: Remove the stated dependency on types.h

All machine/atomic.h necessarily include sys/atomic_common.h, which
brings in types.h.

Reviewed by:	imp, kib
MFC after:	1 week
Differential Revision:	https://reviews.freebsd.org/D38040

share/man/man9/atomic.9

@@ -22,7 +22,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd March 6, 2021
+.Dd January 16, 2023
 .Dt ATOMIC 9
 .Os
 .Sh NAME
@@ -40,7 +40,6 @@
 .Nm atomic_thread_fence
 .Nd atomic operations
 .Sh SYNOPSIS
-.In sys/types.h
 .In machine/atomic.h
 .Ft void
 .Fn atomic_add_[acq_|rel_]<type> "volatile <type> *p" "<type> v"