Update in Rule EC2_SECURITY_GROUP_NOT_USED

Hi,

I would like to report a required update to get the rule EC2_SECURITY_GROUP_NOT_USED created.
I've noticed that the parameters.json is set to python3.6 and this is a runtime no longer supported for lambda. I recommend you to update the file to python3.7 which i tested and works.

If you need any other details, please let me know.