pgsql: Fix the check to limit sync workers.

Fix the check to limit sync workers.

We don't allow to invoke more sync workers once we have reached the sync
worker limit per subscription. But the check to enforce this also doesn't
allow to launch an apply worker if it gets restarted.

This code was introduced by commit de43897122 but we caught the problem
only with the test added by recent commit c91f71b9dc which started failing
occasionally in the buildfarm.

As per buildfarm.
Diagnosed-by: Amit Kapila, Masahiko Sawada, Tomas Vondra
Author: Amit Kapila
Backpatch-through: 10
Discussion: https://postgr.es/m/CAH2L28vddB_NFdRVpuyRBJEBWjz4BSyTB=_ektNRH8NJ1jf95g@mail.gmail.com
https://postgr.es/m/f90d2b03-4462-ce95-a524-d91464e797c8@enterprisedb.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/dd4ab6fd6528e160571986fa8817cee9f2645aa8

Modified Files
--------------
src/backend/replication/logical/launcher.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)