getnameinfo.3 fix markup

NI_NUMERICSERV and NI_DGRAM miss the Dv macro.

Noticed while looking at the HTML version of this manpage.
e.g. https://man.openbsd.org/getnameinfo.3
-- 
:wq Claudio

Index: getnameinfo.3
===================================================================
RCS file: /cvs/src/lib/libc/net/getnameinfo.3,v
diff -u -p -r1.49 getnameinfo.3
--- getnameinfo.3	11 Sep 2022 06:38:10 -0000	1.49
+++ getnameinfo.3	5 Aug 2026 08:06:57 -0000
@@ -99,9 +99,9 @@ If the host name cannot be found in DNS 
 a non-zero error code is returned.
 If the host name is not found and the flag is not set, the
 address is returned in numeric form.
-.It NI_NUMERICSERV
+.It Dv NI_NUMERICSERV
 The service name is returned as a digit string representing the port number.
-.It NI_DGRAM
+.It Dv NI_DGRAM
 Specifies that the service being looked up is a datagram
 service, and causes
 .Xr getservbyport 3