MB-7483: Remove duplicate stats holding bucket size

ep_max_data_size (removed)
ep_max_size

Change-Id: Ie0dd4f94b15917ad397c1902449cd6f193e73c89
Reviewed-on: http://review.couchbase.org/24638
Reviewed-by: Chiyoung Seo <chiyoung.seo@gmail.com>
Tested-by: Michael Wiederhold <mike@couchbase.com>