BUG: Update mjml-browser dependency

[casesolved-co-uk]

GrapesJS version

• I confirm to use the latest version of GrapesJS

GrapesJS MJML version

• I confirm to use the latest version of GrapesJS MJML

What browser are you using?

Chrome 138

Reproducible demo link

https://grapesjs.com/demo-mjml.html

Describe the bug

Current pinned version of mjml-browser: 4.13.0 (3 years ago)

Latest mjml-browser: 4.15.3

Code of Conduct

• I agree to follow this project's Code of Conduct