test: add tests to `ndarray/base/map`

[headlessNode]

Description

What is the purpose of this pull request?

This pull request:

• Adds tests to ndarray/base/map for 100% coverage.

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This pull request:

• none

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• [x] Read, understood, and followed the contributing guidelines.

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@stdlib-js/reviewers

[headlessNode]

@kgryte Please review, thanks!

[kgryte]

Re: failing benchmark workflow. This is due to a timeout. I ran the benchmarks locally and all ran successfully. As such, I'll ignore the workflow failure and go ahead and merge...