Fix link case sensitivity in README.md

[eizedev]

Description

fix url

Related Issue

Motivation and Context

How Has This Been Tested?

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[Copilot]

Pull request overview

This PR updates the README’s benchmark documentation link to use the correct filename casing so it works on case-sensitive filesystems (e.g., Linux).

Changes:

• Fix the res/benchmarks/... README link to point to testing-and-speed.md (lowercase).

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