Improve doc vincent

What does this MR do?

just improved the MLIR installation .md file (docs/BUILD_WITH_MLIR.md)

Related issues

none

Author's checklist

• Follow the Contribution Guidelines. Sign the CLA and add yourself to the list of contribtutors for your first contribution.
• Describe your change in the CHANGELOG.md file in the top-level folder of the openCARP repository.
• Apply the appropriate labels.
• Does this commit add new dependencies? If no, just tick the box. If yes, please evaluate carefully if the additional dependency is a more sustainable option than including the functionality in own code. If the former, describe the dependency clearly, add them to the Software Management Plan and the installation instructions (*.md files, CMake files, Docker files etc.).

Reviewer's checklist

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Reviewer

minor doc fix.

Maintainer