Suppress warning and stdout messages in Jupyter notebooks #2421

Job	Run time
static_checks	46s
link_checker	10s
build_and_test_py_standalone	2m 2s
build_and_test_nest_desktop (master)	11m 8s
build_and_test_nest_compartmental (master)	18m 53s
build_and_test_nest (v2.20.2)	27m 53s
build_and_test_nest (v3.0)	21m 41s
build_and_test_nest (v3.8)	23m 4s
build_and_test_nest (master)	46m 34s
	2h 32m 11s

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