fix run_evaluate_episodes parameter

[DrRyanHuang]

Hi, thx for PARL's good work!

The second para of run_evaluate_episodes is eval_episodes: int, so we don't need env.

And it will raise 'CompatWrapper' object cannot be interpreted as an integer in the 55th line of examples/QuickStart/train.py.

By the way, I add the cli --eval.

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you all sign our Contributor License Agreement before we can accept your contribution.
1 out of 2 committers have signed the CLA.

✅ DrRyanHuang
❌ TomorrowIsAnOtherDay
_{You have signed the CLA already but the status is still pending? Let us recheck it.}