doc: remove outdated sentence

[lpinca]

The 'IPv4' and 'IPv6' values are no longer supported.

Fixes: #54961

[nodejs-github-bot]

Review requested:

• @nodejs/net

[aduh95]

Can we add an entry in the YAML list?

[lpinca]

The current documentation is correct

$ ./node
Welcome to Node.js v23.0.0-pre.
Type ".help" for more information.
> dns.lookup('example.com', { family: 'IPv4' }, function (err, result) { console.log(result) })
GetAddrInfoReqWrap {
  callback: [Function (anonymous)],
  family: 4,
  hostname: 'example.com',
  oncomplete: [Function: onlookup]
}
> 93.184.215.14

The 'IPv4' and 'IPv6' values are not supported in the promise returning variant, but that is also correctly documented.

[avivkeller]

However the deprecation has reached End-Of-Life per #41431, so maybe that behavior should be changed?

[aduh95]

See #43054. It might make sense to update deprecations.md to clarify dns.lookup is no longer in scope.