np.float is deprecated

[dachengx]

What is the problem / what does the code in this PR do

Using the aliases of builtin types like np.int is deprecated

reference: https://numpy.org/devdocs/release/1.20.0-notes.html#deprecations

In principle the auto tests in XENONnT/base_environment#1483 will not pass, but the line changed in this PR was never checked:

Can you briefly describe how it works?

Can you give a minimal working example (or illustrate with a figure)?

Please include the following if applicable:

• Update the docstring(s)
• Update the documentation
• Tests to check the (new) code is working as desired.
• Does it solve one of the open issues on github?

Please make sure that all automated tests have passed before asking for a review (you can save the PR as a draft otherwise).

[github-actions]

coverage: 91.352%. remained the same
when pulling 8d33de1 on deprecated_float
into 7396d79 on master.

[coveralls]

coverage: 91.062% (-0.3%) from 91.352%
when pulling 8d33de1 on deprecated_float
into 7396d79 on master.

[WenzDaniel]

Thanks Dacheng