Unordered wait event ClogGroupUpdate

Hi all,

baaf272 has added support for group updates in clog, however it has
added the wait event WAIT_EVENT_CLOG_GROUP_UPDATE in a non-alphabetical
order.  There are many events, so keeping things in order helps users in
finding them.

Are there any objections to the attached, which reorders things
properly?  This is a patch for HEAD, for v11 I propose to only fix the
documentation side of things to avoid an ABI breakage.

I checked the other wait events and things are in order.

Thanks,
--
Michael