docs: improve doctests for complex number instances in math/base/special/cceiln/

[sujalc879]

Resolves #8641 .

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@stdlib-js/reviewers

[stdlib-bot]

Hello! 👋

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[sujalc879]

also made changes in lib/node_modules/@stdlib/math/base/special/cceiln/README.md take a look once

[stdlib-bot]

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