LU-18957 tests: remove obsolete osc.*.contention_seconds

LU-18957 tests: remove obsolete osc.*.contention_seconds

Remove the obsolete parameter osc.*.contention_seconds from
sanity.sh and sanityn.sh.

Test-Parameters: trivial
Fixes: 5ad00e36eca1 ("LU-14838 osc: Remove client contention support")

Signed-off-by: Emoly Liu <emoly@whamcloud.com>
Change-Id: Ie62157adfe7588fa66f9e82d97affee8ad2d4436
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/58998
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Patrick Farrell <pfarrell@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>