Fix testConvertComparison test in TestPostgreSqlClient #63033

Job	Run time
check-commits-dispatcher	1m 8s
hive-tests (config-hdp3)	1m 11s
error-prone-checks	3m 7s
artifact-checks	17m 29s
maven-checks 21	14m 21s
maven-checks 22	14m 42s
test-jdbc-compatibility	2m 54s
test-other-modules	6m 32s
maven-checks 23-ea	18m 41s
web-ui-checks	1m 7s
build-pt	8m 35s
build-test-matrix	1m 15s
check-commit	1s
test (plugin/trino-postgresql)	8m 19s
test (testing/trino-faulttolerant-tests, default)	4m 56s
test (testing/trino-faulttolerant-tests, test-fault-tolerant-delta)	5m 27s
test (testing/trino-faulttolerant-tests, test-fault-tolerant-hive)	13m 43s
test (testing/trino-faulttolerant-tests, test-fault-tolerant-iceberg)	10m 12s
pt (default, suite-7-non-generic, )	21m 41s
pt (default, suite-all-connectors-smoke, )	2m 57s
	2h 38m 18s

Provide feedback