test: Fix database metadata to handle older versions for function comment

Fixes DatabaseMetaDataTest to use older syntax for COMMENT ON FUNCTION with
explicit no-arg parameter parentheses as it is required on server versions
before v10.

Author: sehrope

pgjdbc/src/test/java/org/postgresql/test/jdbc2/DatabaseMetaDataTest.java

@@ -92,7 +92,7 @@ public void setUp() throws Exception {
     TestUtil.createTable(con, "duplicate", "x text");
     TestUtil.execute("comment on table duplicate is 'duplicate table'", con);
     TestUtil.execute("create or replace function bar() returns integer language sql as $$ select 1 $$", con);
-    TestUtil.execute("comment on function bar is 'bar function'", con);
+    TestUtil.execute("comment on function bar() is 'bar function'", con);
     TestUtil.execute("update pg_description set objoid = 'duplicate'::regclass where objoid = 'bar'::regproc",conPriv);
 
     // 8.2 does not support arrays of composite types