doc: dns.lookup() documentation error code

dns.lookup() will always return ENOTFOUND on a empty lookup
or when the host not found.
https://github.com/nodejs/node/blob/master/lib/internal/errors.js#L503

Fixes: nodejs#27604

PR-URL: nodejs#27625
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

doc/api/dns.md

@@ -168,7 +168,7 @@ With the `all` option set to `true`, the arguments for `callback` change to
 properties `address` and `family`.
 
 On error, `err` is an [`Error`][] object, where `err.code` is the error code.
-Keep in mind that `err.code` will be set to `'ENOENT'` not only when
+Keep in mind that `err.code` will be set to `'ENOTFOUND'` not only when
 the hostname does not exist but also when the lookup fails in other ways
 such as no available file descriptors.
 
@@ -692,7 +692,7 @@ being an array of objects with the properties `address` and `family`.
 
 On error, the `Promise` is rejected with an [`Error`][] object, where `err.code`
 is the error code.
-Keep in mind that `err.code` will be set to `'ENOENT'` not only when
+Keep in mind that `err.code` will be set to `'ENOTFOUND'` not only when
 the hostname does not exist but also when the lookup fails in other ways
 such as no available file descriptors.