refactor: remove unnecessary variable declaration from blas/ext/base/dnannsumkbn2

[headlessNode]

Description

What is the purpose of this pull request?

This pull request:

• remove unnecessary variable declarations in addon.c
• suppress C lint warning form benchmark.length.c

Related Issues

Does this pull request have any related issues?

No.

Questions

Any questions for reviewers of this pull request?

No.

Other

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No.

Checklist

Please ensure the following tasks are completed before submitting this pull request.

• Read, understood, and followed the contributing guidelines.

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@stdlib-js/reviewers

[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
blas/ext/base/dnannsumkbn2	$\color{red}438/442$ $\color{green}+99.09\%$	$\color{red}24/25$ $\color{green}+96.00\%$	$\color{green}4/4$ $\color{green}+100.00\%$	$\color{red}438/442$ $\color{green}+99.09\%$

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

[kgryte]

@headlessNode Thank you for following up on this. LGTM.