Fix jsonb_plpython tests on older Python versions

Rewrite one test to avoid a case where some Python versions have output
format differences (Decimal('1') vs Decimal("1")).

contrib/jsonb_plpython/expected/jsonb_plpython.out

@@ -6,11 +6,10 @@ LANGUAGE plpythonu
 TRANSFORM FOR TYPE jsonb
 AS $$
 assert isinstance(val, dict)
-plpy.info(sorted(val.items()))
+assert(val == {'a': 1, 'c': 'NULL'})
 return len(val)
 $$;
 SELECT test1('{"a": 1, "c": "NULL"}'::jsonb);
-INFO:  [('a', Decimal('1')), ('c', 'NULL')]
  test1 
 -------
      2

contrib/jsonb_plpython/sql/jsonb_plpython.sql

@@ -6,7 +6,7 @@ LANGUAGE plpythonu
 TRANSFORM FOR TYPE jsonb
 AS $$
 assert isinstance(val, dict)
-plpy.info(sorted(val.items()))
+assert(val == {'a': 1, 'c': 'NULL'})
 return len(val)
 $$;