Tech debt: update numpy dtypes to avoid deprecation errors

[monocongo]

How to craft a useful, minimal bug report

Describe the bug In order to get tests passing again we need to fix various issues such as this:

FAILED tests/test_utils.py::test_transform_to_366day - AttributeError: module 'numpy' has no attribute 'float'. np.float was a deprecated alias for the builtin float. To avoid this error in existing code, use float by itself. Doing this will not modify any behavior and is safe. If you specifically wanted the numpy scalar type, use np.float64 here.

To Reproduce Make a pull request and watch as the tests fail due to this sort of tech debt.

Expected behavior Tests will pass for Python 3.7 -> 3.11

Screenshots If applicable, add screenshots to help explain your problem.

Desktop (please complete the following information):

• OS: [e.g. iOS]
• Version: [e.g. 22]

Additional context Add any other context about the problem here.