Improve the docstring of the expect macro #344

Job	Run time
Build and test (24.4)	27s
Build and test (24.5)	26s
Build and test (25.1)	27s
Build and test (25.2)	26s
Build and test (25.3)	26s
Build and test (26.1)	26s
Build and test (26.2)	26s
Build and test (26.3)	27s
Build and test (27.1)	27s
Build and test (28.1)	30s
Build and test (28.2)	27s
Build and test (29.1)	33s
Build and test (29.2)	38s
Build and test (29.3)	45s
Build and test (29.4)	38s
Build and test (release-snapshot)	39s
Build and test (snapshot)	28s
	8m 36s

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