pad: Revert back to sending `CLIENT_READY` on reconnect
pad: Revert back to sending `CLIENT_READY` on reconnect

Commit 0bb8d73ba2969bc2c871c5095de19188a75b2b54 fixed the author ID
that is saved in the socket.io sessioninfo when the client sends a
`CLIENT_READY` with `reconnect` set to true, so it is now safe to undo
the workaround from PR #3868.

Fixes #4331.

storytouch/etherpad-lite,ether/etherpad-lite,storytouch/etherpad-lite,ether/etherpad-lite,storytouch/etherpad-lite,ether/etherpad-lite