`integrate` function never uses

it appears that the `integrate` function is yet never used. 
parameters could allign better with the given data structure of vitabel

consider refactor or eliminate

https://github.com/UniGrazMath/vitabel/blame/fc0450c2a3be83a328af3bd77cb10b93747c3158/src/vitabel/utils/helpers.py#L156-L184