test: migrate math/base/special/atan to ULP-based testing

[yb175]

Resolves #11352.

Description

What is the purpose of this pull request?

This pull request:

• Migrates math/base/special/atan native tests from relative-tolerance assertions to ULP-based assertions using @stdlib/assert/is-almost-same-value.

Related Issues

Does this pull request have any related issues?

This pull request has the following related issues:

• [RFC]: Migrate math/base/special packages from relative tolerance testing to ULP difference testing (tracking issue) #11352

Questions

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No.

Other

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No.

Checklist

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• Read, understood, and followed the contributing guidelines.

AI Assistance

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Coverage Report

Package	Statements	Branches	Functions	Lines
math/base/special/atan	$\\color{green}346/346$ $\\color{green}+100.00\\%$	$\\color{green}33/33$ $\\color{green}+100.00\\%$	$\\color{green}4/4$ $\\color{green}+100.00\\%$	$\\color{green}346/346$ $\\color{green}+100.00\\%$

The above coverage report was generated for the changes in this PR.