qa/suites/crimson-rados/../pggrow: increase op_delay

qa/suites/crimson-rados/../pggrow: increase op_delay

Increase op_delay to pggrow to avoid rapid PG splits.
Excessive splitting with a low reactor count can leave many PGs in
snaptrim, causing tests to hit the (short) snap trimming timeout.

Crimson's pggrow keeps the OSDs clean thorugout the entire test,
which is against do_thrash expectations.
Increasing op_delay would reduce do_thrash "actions" back to a normal rate.

Fixes: https://tracker.ceph.com/issues/75273
Signed-off-by: Matan Breizman <mbreizma@redhat.com>