Fix `plugin` switch #645

Job	Run time
lint_and_docs (ubuntu-22.04, 3.9, 20.x)	8m 34s
build_js (ubuntu-22.04, 3.9, 20.x)	27m 2s
build_emscripten_wheel (ubuntu-22.04, x86_64, 3.9, 20.x)	18m 4s
build_python (ubuntu-22.04, x86_64, 3.9, 20.x, false)	17m 40s
build_and_test_rust (ubuntu-22.04, x86_64, 20.x, false)	10m 7s
test_python (ubuntu-22.04, x86_64, 3.9, 20.x, false)	1m 20s
test_js (ubuntu-22.04, 3.9, 20.x)	5m 27s
build_and_test_jupyterlab (ubuntu-22.04, x86_64, 3.9, 20.x, false)	1m 15s
benchmark_python	0s
benchmark_js	0s
test_python_sdist (ubuntu-22.04, x86_64, 3.9)	9m 48s
publish	0s
	1h 39m 17s

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