docs: improve doctests for ndarray instances in `stats/cumin` #24851

Job	Run time
Manage labels	0s
Auto-fix lint errors	0s
Merge changes from develop branch into this PR	0s
Remove in-progress label	0s
Check for required files	-5s
Update copyright header years	-7s
Rebase this PR on top of develop branch	-8s
	-20s

Provide feedback