Doc: Fix pg_copy_logical_replication_slot description.
This commit documents that the failover option is not copied when using
the pg_copy_logical_replication_slot function.
In passing, we modify the comments in the function clarifying the reason
for this behavior.
Reported-by: <duffieldzane@gmail.com>
Author: Hou Zhijie <houzj.fnst@fujitsu.com>
Reviewed-by: Amit Kapila <amit.kapila16@gmail.com>
Backpatch-through: 17, where it was introduced
Discussion: https://postgr.es/m/
173976850802.682632.
11315364077431550250@wrigleys.postgresql.org