Fix broken links

[mccoyp]

Description

Resolves nightly build errors related to the recent azure-sdk-tools move.

All SDK Contribution checklist:

• The pull request does not introduce [breaking changes]
• CHANGELOG is updated for new features, bug fixes or other significant changes.
• I have read the contribution guidelines.

General Guidelines and Best Practices

• Title of the pull request is clear and informative.
• There are a small number of commits, each of which have an informative message. This means that previously merged commits do not appear in the history of the PR. For more information on cleaning up the commits in your PR, see this page.

Testing Guidelines

• Pull request includes test coverage for the included changes.

[Copilot]

Pull Request Overview

This PR fixes broken links in documentation that were caused by a recent azure-sdk-tools move, addressing nightly build errors. The changes update GitHub URLs with outdated commit hashes and line numbers to point to the correct locations in the codebase.

Key Changes

• Updates commit hashes and line numbers in GitHub links to reflect current code locations
• Removes an outdated reference to a deleted cheat sheet file
• Ensures documentation links remain functional after the azure-sdk-tools reorganization

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
eng/tools/azure-sdk-tools/devtools_testutils/README.md	Updates 6 GitHub links with new commit hashes and corrected line numbers
doc/dev/tests.md	Updates 2 GitHub links to fix broken references to test utilities
doc/dev/mgmt/README.md	Removes broken reference to deleted cheat sheet file

Comments suppressed due to low confidence (1)

doc/dev/mgmt/README.md:5

• The removal of the cheat sheet reference leaves the sentence 'The page contains a quick reminder...' incomplete and grammatically incorrect. Consider updating the sentence to maintain proper documentation flow.

In order of workflow: