RFR: update code-owners

[Phil Race]

I just happened to notice the guide still has the old 5 retired client mailing lists instead of the client-libs-dev replacement

Then I noticed the code area assignments were out of date too.

-------------

Commit messages:
 - update code-owners

Changes: https://git.openjdk.java.net/guide/pull/84/files
 Webrev: https://webrevs.openjdk.java.net/?repo=guide&pr=84&range=00
  Stats: 19 lines in 1 file changed: 0 ins; 13 del; 6 mod
  Patch: https://git.openjdk.java.net/guide/pull/84.diff
  Fetch: git fetch https://git.openjdk.java.net/guide pull/84/head:pull/84

PR: https://git.openjdk.java.net/guide/pull/84