pgsql: Disable debug_discard_caches in test_oat_hooks test.

Disable debug_discard_caches in test_oat_hooks test. The test output varies when debug_discard_caches is enabled, because that causes extra executions of recomputeNamespacePath. Maybe putting a hook in that was a bad idea, but as a stopgap, just turn off debug_discard_caches in this test. Per bui

pgsql: Disable debug_discard_caches in test_oat_hooks test.

Disable debug_discard_caches in test_oat_hooks test. The test output varies when debug_discard_caches is enabled, because that causes extra executions of recomputeNamespacePath. Maybe putting a hook in that was a bad idea, but as a stopgap, just turn off debug_discard_caches in this test. Per bui