pacific: doc/rados: update config for autoscaler

[zdover23]

Update doc/rados/configuration/pool-pg-config-ref.rst to account for the behavior of autoscaler.

Previously, this file was last meaningfully altered in 2013, prior to the invention of autoscaler. A recent confusion was brought to my attention on the Ceph Slack whereby a user attempted to alter the default values of a Quincy cluster, as suggested in this documentation. That alteration caused Ceph to throw the error "Error ERANGE: 'pgp_num' must be greater than 0 and lower or equal than 'pg_num', which in this case is one" and a related "rgw_init_ioctx ERROR" reading in part "Numerical result out of range". The user removed the "osd_pool_default_pgp_num" configuration line from ceph.conf and the cluster worked as expected. I presume that this is because the removal of this configuration line allowed autoscaler to work as intended.

Fixes: https://tracker.ceph.com/issues/64259

Co-authored-by: David Orman ormandj@corenode.com
Signed-off-by: Zac Dover zac.dover@proton.me
(cherry picked from commit 4dc1209)

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