Increase max connection for replica to prevent test flukyness (#10306)

## Problem

See #10167
Too small number of `max_connections` (2) can cause failures of
test_physical_replication_config_mismatch_too_many_known_xids test

## Summary of changes

Increase `max_connections` to 5

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

test_runner/regress/test_physical_replication.py

@@ -187,7 +187,7 @@ def test_physical_replication_config_mismatch_too_many_known_xids(neon_simple_en
         origin=primary,
         endpoint_id="secondary",
         config_lines=[
-            "max_connections=2",
+            "max_connections=5",
             "autovacuum_max_workers=1",
             "max_worker_processes=5",
             "max_wal_senders=1",