Some corrections to RELEASE-NOTES-1.23

* Fixed a typo: "When $wgJobRunRate is higher that zero [...]".
* Removed a reference to 1.22: "[...] not yet queried but will be
  in a future point release of 1.22."
* Fixed misspellings "wiki's" and "sql" in the same note.

Change-Id: I5fee88c459345ecd8b71f9e5b86c65afae183ba1