Update flutter_math_fork

[edhom]

Description

This updates flutter_math_fork to the latest version.

Related issues & PRs

n/a

Checklist

• I have made myself familiar with the CaTeX
  contributing guide.
• I added a PR description.
• I linked all related issues and PRs I could find (no links if there are none).
• If this PR changes anything about the main math_keyboard or example package
  (also README etc.), I created an entry in CHANGELOG.md (## UPCOMING RELEASE if the change
  on its own is not worth an update).
• If this PR includes a notable change in the math_keyboard package, I updated the version
  according to Dart's semantic versioning.
• If there is new functionality in code, I added tests covering all my additions.
• All required checks pass.

[creativecreatorormaybenot]

🚀

Two things that need to be done:

1. Changelog entry
2. Tests are failing on stable after the change 🤔

[edhom]

@creativecreatorormaybenot Oh I thought we don't add an entry for patches:D
The test were failing cause the latest version of flutter_svg is used, which requires flutter 2.5 iirc (see the use of LayerHandle). But the flutter-action workflow used in the checks used an old flutter version. Updating it fixed it:)

[creativecreatorormaybenot]

LGTM 🚀