Update tests in runtests.jl for perfect-numbers

[depial]

Adds six tests which require the functions to return false, supplementing the previous testing whose inputs returned true, resolving this issue

[github-actions[bot]]

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[ErikSchierboom]

Thanks for this! I'll let @cmcaine take a quick look too, but LGTM!

[ErikSchierboom]

Merged, thanks!

[cmcaine]

Thanks!