update prompts for open orca to match the paper (#317)

fix the test for the updated system tokenizer

tests/test_prompters.py

@@ -70,7 +70,7 @@ class AlpacaPrompterTest(unittest.TestCase):
             )
         )
         assert "use cot" in res
-        assert res.startswith("use cot")
+        assert res.startswith("### System:")
         assert "### Instruction:" not in res
         assert "### Input:" not in res
         assert "alpacas" in res