Update middleman from 4.3.12-pre to 4.4.0

Why is this change being made?

The latest middleman (middleman, middleman-cli, middlman-core gems) in 4.x (4.4.0) now officially supports Ruby 3.0.

Diff in the upstream: https://github.com/middleman/middleman/compare/d180ca3...ae9c4bd

Author Checklist

• Provided a concise title for the MR
• Added a description to this MR explaining the reasons for the proposed change, per say-why-not-just-what
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Closes #11983 (closed)