Update README.md

[ahcorde]

🦟 Documentation fix

Fixes gazebosim/gazebo_test_cases#71

Summary

Fixed links

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
• While waiting for a review on your PR, please help review another open pull request to support the maintainers

Note to maintainers: Remember to use Squash-Merge and edit the commit message to match the pull request summary while retaining Signed-off-by messages.

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (gz-gui8@181a0d5). Click here to learn what that means.
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❗ Current head d54733d differs from pull request most recent head 3fc7215. Consider uploading reports for the commit 3fc7215 to get more accurate results

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