Bump version number to 0.5.0 #1241

Job	Run time
build-wheels	11s
build-binder-env	10s
build-test-env-base	1m 21s
build-notebooks	8s
run-mypy	34s
run-black-check	17s
run-pylint	31s
test-wheels	18s
test-with-botocore-and-coverage	23s
check-docs	22s
	4m 15s

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