MB-7483: Remove duplicate stats holding bucket size

ep_max_data_size (removed)
ep_max_size

Change-Id: Ia29539cdef796961a240064e95375a3020dce760
Reviewed-on: http://review.couchbase.org/26945
Reviewed-by: Michael Wiederhold <mike@couchbase.com>
Tested-by: Michael Wiederhold <mike@couchbase.com>