Change cupy installation prints to debug logs

[yousefmoazzam]

Fixes #301

Acceptance criteria checklist:

• [x] In conjunction with the tentative fix to launcher issue https://gitlab.diamond.ac.uk/scisoft/tomography/httomo_dls/-/issues/23, the print statement of "CuPy is not installed" when running the launcher on wilson doesn't appear

Before change:

(/dls/science/users/twi18192/conda-envs/httomo) [twi18192@cs04r-sc-vserv-300 httomo (log-cupy-install-info)]$ python -m httomo_dls.launcher
CuPy is not installed
Usage: python -m httomo_dls.launcher [OPTIONS] IN_DATA_FILE YAML_CONFIG
                                     OUT_DIR
Try 'python -m httomo_dls.launcher --help' for help.

Error: Missing argument 'IN_DATA_FILE'.

After change:

(/dls/science/users/twi18192/conda-envs/httomo) [twi18192@cs04r-sc-vserv-300 httomo (log-cupy-install-info)]$ python -m httomo_dls.launcher
Usage: python -m httomo_dls.launcher [OPTIONS] IN_DATA_FILE YAML_CONFIG
                                     OUT_DIR
Try 'python -m httomo_dls.launcher --help' for help.

Error: Missing argument 'IN_DATA_FILE'.