Do not fix patch level version for dependency on ctapipe

[jlenain]

Describe the bug
Currently, our dependency on ctapipe is pinned to v0.19.1.

To Reproduce
Steps to reproduce the behavior:

1. mamba env create -n nectarchain -c conda-forge -f environment.list
2. mamba activate nectarchain
3. mamba list ctapipe

Expected behavior
We should not depend on pinned patch level, but instead let the last patch of ctapipe be installed on mamba env create/mamba update.