Use sycnhronous commit for logical replicaiton worker (#8645)

## Problem

See
https://neondb.slack.com/archives/C03QLRH7PPD/p1723038557449239?thread_ts=1722868375.476789&cid=C03QLRH7PPD


Logical replication subscription by default use `synchronous_commit=off`
which cause problems with safekeeper

## Summary of changes

Set `synchronous_commit=on` for logical replication subscription in
test_subscriber_restart.py

## Checklist before requesting a review

- [ ] I have performed a self-review of my code.
- [ ] If it is a core feature, I have added thorough tests.
- [ ] Do we need to implement analytics? if so did you add the relevant
metrics to the dashboard?
- [ ] If this PR requires public announcement, mark it with
/release-notes label and add several sentences in this section.

## Checklist before merging

- [ ] Do not forget to reformat commit message to not include the above
checklist

---------

Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>
Co-authored-by: Heikki Linnakangas <heikki@neon.tech>

test_runner/regress/test_subscriber_restart.py

@@ -37,7 +37,9 @@ def test_subscriber_restart(neon_simple_env: NeonEnv):
             scur.execute("CREATE TABLE t (pk integer primary key, sk integer)")
             # scur.execute("CREATE INDEX on t(sk)") # slowdown applying WAL at replica
             pub_conn = f"host=localhost port={pub.pg_port} dbname=postgres user=cloud_admin"
-            query = f"CREATE SUBSCRIPTION sub CONNECTION '{pub_conn}' PUBLICATION pub"
+            # synchronous_commit=on to test a hypothesis for why this test has been flaky.
+            # XXX: Add link to the issue
+            query = f"CREATE SUBSCRIPTION sub CONNECTION '{pub_conn}' PUBLICATION pub with (synchronous_commit=on)"
             scur.execute(query)
             time.sleep(2)  # let initial table sync complete