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

@@ -1784,7 +1784,7 @@ additional details.
 <a id="ERR_TLS_CERT_ALTNAME_INVALID"></a>
 ### `ERR_TLS_CERT_ALTNAME_INVALID`
 
-While using TLS, the hostname/IP of the peer did not match any of the
+While using TLS, the host name/IP of the peer did not match any of the
 `subjectAltNames` in its certificate.
 
 <a id="ERR_TLS_DH_PARAM_SIZE"></a>
@@ -1835,7 +1835,7 @@ An attempt was made to renegotiate TLS on a socket instance with TLS disabled.
 ### `ERR_TLS_REQUIRED_SERVER_NAME`
 
 While using TLS, the `server.addContext()` method was called without providing
-a hostname in the first parameter.
+a host name in the first parameter.
 
 <a id="ERR_TLS_SESSION_ATTACK"></a>
 ### `ERR_TLS_SESSION_ATTACK`