Add more precise wording to the pthread_rwlockattr_init(3) synopsis

OK tb@

Author: job

lib/libpthread/man/pthread_rwlockattr_init.3

@@ -1,4 +1,4 @@
-.\" $OpenBSD: pthread_rwlockattr_init.3,v 1.10 2025/06/07 00:16:52 schwarze Exp $
+.\" $OpenBSD: pthread_rwlockattr_init.3,v 1.11 2025/06/20 12:51:51 job Exp $
 .\" Copyright (c) 1998 Alex Nash
 .\" All rights reserved.
 .\"
@@ -25,12 +25,12 @@
 .\"
 .\" $FreeBSD: pthread_rwlockattr_init.3,v 1.3 1999/08/28 00:03:10 peter Exp $
 .\"
-.Dd $Mdocdate: June 7 2025 $
+.Dd $Mdocdate: June 20 2025 $
 .Dt PTHREAD_RWLOCKATTR_INIT 3
 .Os
 .Sh NAME
 .Nm pthread_rwlockattr_init
-.Nd initialize a read/write lock
+.Nd initialize a read/write lock attributes object
 .Sh SYNOPSIS
 .Lb libpthread
 .In pthread.h