LU-17831 llite: remove refcount assert

LU-17831 llite: remove refcount assert

This refcount assert costs us a few % in page freeing and
it comes immediately after a dec_and_test.

Signed-off-by: Patrick Farrell <patrick.farrell@oracle.com>
Change-Id: I8de3369cbbaf484e1e0fce27ae3e62cad1ae5282
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/55054
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>