Bump sphinx-rtd-theme from 2.0.0 to 3.0.0 #428

Job	Run time
cwltest release test	3m 50s
CI linters via Tox (lintreadme)	29s
CI tests via Tox (3, 8, lint)	15s
CI linters via Tox (pydocstyle)	14s
CI tests via Tox (3, 8, unit)	1m 6s
CI tests via Tox (3, 8, mypy)	36s
CI tests via Tox (3, 8, bandit)	13s
CI tests via Tox (3, 9, lint)	13s
CI tests via Tox (3, 9, unit)	1m 18s
CI tests via Tox (3, 9, mypy)	35s
CI tests via Tox (3, 9, bandit)	22s
CI tests via Tox (3, 10, lint)	14s
CI tests via Tox (3, 10, unit)	1m 11s
CI tests via Tox (3, 10, mypy)	33s
CI tests via Tox (3, 10, bandit)	21s
CI tests via Tox (3, 11, lint)	19s
CI tests via Tox (3, 11, unit)	1m 12s
CI tests via Tox (3, 11, mypy)	27s
CI tests via Tox (3, 11, bandit)	21s
CI tests via Tox (3, 12, lint)	18s
CI tests via Tox (3, 12, unit)	1m 39s
CI tests via Tox (3, 12, mypy)	50s
CI tests via Tox (3, 12, bandit)	15s
CI tests via Tox (3, 13, lint)	22s
CI tests via Tox (3, 13, unit)	1m 37s
CI tests via Tox (3, 13, mypy)	51s
CI tests via Tox (3, 13, bandit)	26s
	20m 7s

Provide feedback