Fixed bug in simulate_randomized_trial

[jroessler]

Proposed changes

Fixed bug in simulated_randomized_trial (Issue #361) . Changed b*(X) from max{Xi1 +Xi2 + Xi3,0} + max{Xi4 +Xi5,0} to
max{Xi1 +Xi2 , Xi3,0} + max{Xi4 +Xi5,0}. I also added the simulate_randomized_trial method in test_get_synthetic_preds.

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Update (if none of the other choices apply)

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[paullo0106]

LGTM, thanks for the fix