Update release metadata for 2.4.0 GA

Change-Id: I8158659af39b5664a9afed1b3092019d81ea53f1
Reviewed-on: http://review.couchbase.org/40015
Reviewed-by: Brett Lawson <brett19@gmail.com>
Reviewed-by: Matt Ingenthron <matt@couchbase.com>
Tested-by: Mark Nunberg <mnunberg@haskalah.org>