doc: standardize on "host name" in net.md

Our docs have a mix of "hostname" and "host name" in prose.

Let's follow the usage of Unix man pages, RFCs, and most
professionally-edited sources, and use "host name" in prose and
"hostname" to refer to the command and in code.

Lint rule forthcoming.

PR-URL: #31326
Refs: #31073
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>

doc/api/net.md

@@ -503,13 +503,13 @@ changes:
     description: The `host` parameter is supported now.
 -->
 
-Emitted after resolving the hostname but before connecting.
+Emitted after resolving the host name but before connecting.
 Not applicable to Unix sockets.
 
 * `err` {Error|null} The error object. See [`dns.lookup()`][].
 * `address` {string} The IP address.
 * `family` {string|null} The address type. See [`dns.lookup()`][].
-* `host` {string} The hostname.
+* `host` {string} The host name.
 
 ### Event: `'ready'`
 <!-- YAML