Change Online#TimeActivity validations to better match API requirements

Currently Online#TimeActivity enforces a validation that doesn't match up to the API. This change makes the validations more closely match up to what the API requires. This based on what [the documentation]( https://developer.intuit.com/docs/0025_quickbooksapi/0050_data_services/v2/0400_quickbooks_online/timeactivity) says and lots of test requests.