Small docstring fix #336

Job	Run time
Documentation	2m 34s
Julia lts - windows-latest - default - pull_request	1m 48s
Julia lts - ubuntu-latest - x86 - pull_request	1m 30s
Julia lts - macos-latest - default - pull_request	1m 9s
Julia 1 - ubuntu-latest - default - pull_request	3m 47s
Julia lts - ubuntu-latest - default - pull_request	1m 8s
Julia min - ubuntu-latest - x64 - pull_request	59s
Julia 1 - windows-latest - x86 - pull_request	4m 38s
Julia 1 - macos-latest - default - pull_request	2m 24s
Julia 1 - windows-latest - default - pull_request	4m 22s
Julia lts - windows-latest - x86 - pull_request	2m 20s
Julia 1 - ubuntu-latest - x86 - pull_request	4m 24s
	31m 3s

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