doc/rados: remove HitSet-related key information
Remove HitSet-related key information from
doc/rados/operations/pools.rst. HitSet-related keys are relevant only to
releases of Ceph that support cache tiering. Only Quincy and earlier
(inclusive) releases of Ceph support cache tiering. Backport this commit
from main to Reef, but not to Quincy or to release branches earlier than
Quincy.
Signed-off-by: Zac Dover <zac.dover@proton.me>
(cherry picked from commit
78878511a3e782d5cde63bfb71409c46244402f7)