pgsql: Fix excessive logging in idle slotsync worker.

Fix excessive logging in idle slotsync worker.

The slotsync worker was incorrectly identifying no-op states as successful
updates, triggering a busy loop to sync slots that logged messages every
200ms. This patch corrects the logic to properly classify these states,
enabling the worker to respect normal sleep intervals when no work is
performed.

Reported-by: Fujii Masao <masao.fujii@gmail.com>
Author: Zhijie Hou <houzj.fnst@fujitsu.com>
Reviewed-by: Amit Kapila <amit.kapila16@gmail.com>
Reviewed-by: shveta malik <shveta.malik@gmail.com>
Backpatch-through: 17, where it was introduced
Discussion: https://postgr.es/m/CAHGQGwF6zG9Z8ws1yb3hY1VqV-WT7hR0qyXCn2HdbjvZQKufDw@mail.gmail.com

Branch
------
REL_18_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/540fe8fb5c22a6c724513f62daaae79af5d559cb

Modified Files
--------------
src/backend/replication/logical/slotsync.c | 17 +++++++++++++++--
1 file changed, 15 insertions(+), 2 deletions(-)