remove warning for missing dependencies for main darts package #4351

Job	Run time
docs	14m 6s
lint	1m 1s
check-examples (03-FFT-examples.ipynb)	6m 25s
tests (macos-latest, 3.9, all)	52m 33s
check-examples (04-RNN-examples.ipynb)	10m 12s
tests (ubuntu-latest, 3.9, all)	36m 53s
check-examples (00-quickstart.ipynb)	8m 38s
check-examples (02-data-processing.ipynb)	8m 13s
check-examples (01-multi-time-series-and-covariates.ipynb)	9m 20s
	2h 27m 21s

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