mupdf: migrate to brewed X11

[gromgit]

Also fixed license. Supports #64166.

• Have you followed the guidelines for contributing?
• Have you checked that there aren't other open pull requests for the same formula update/change?
• Have you built your formula locally with brew install --build-from-source <formula>, where <formula> is the name of the formula you're submitting?
• Is your test running fine brew test <formula>, where <formula> is the name of the formula you're submitting?
• Does your build pass brew audit --strict <formula> (after doing brew install <formula>)?

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• brew install FORMULA on this list (should be poured from a bottle, not built from source)
• Run brew linkage FORMULA and observe which X11 libraries it links against
• Modify the formula to remove depends_on :x11 and replace it with e.g. depends_on "libx11" and any additional X libraries
• Update /opt/X11 or MacOS::XQuartz references to instead point them to the brewed formula paths
• revision bump
• brew install -s FORMULA and brew linkage FORMULA to check that it's now linking against brewed X and not XQuartz

[BrewTestBot]

🤖 A scheduled task has triggered a merge.