doc: standardize on "host name" in deprecations.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/deprecations.md

@@ -2270,7 +2270,7 @@ The `_handle` property has been removed because improper use of the native
 object can lead to crashing the application.
 
 <a id="DEP0118"></a>
-### DEP0118: `dns.lookup()` support for a falsy hostname
+### DEP0118: `dns.lookup()` support for a falsy host name
 <!-- YAML
 changes:
   - version: v11.0.0
@@ -2280,7 +2280,7 @@ changes:
 
 Type: Runtime
 
-Previous versions of Node.js supported `dns.lookup()` with a falsy hostname
+Previous versions of Node.js supported `dns.lookup()` with a falsy host name
 like `dns.lookup(false)` due to backward compatibility.
 This behavior is undocumented and is thought to be unused in real world apps.
 It will become an error in future versions of Node.js.