Upgrade saxon-js version (source: 18F/fedramp-automation: 707)

[danielnaab]

Original issue: https://github.com/18F/fedramp-automation/issues/707

Upgrade saxon-js to latest version.

Definition of Done

• [ ] Acceptance criteria met
• [ ] Unit test coverage of our code > 90% - needs automation story
• [ ] Accessibility tests pass - needs automation story
• [ ] Automated code quality checks pass
• [ ] Security reviewed and reported - check in with Wes on what we could do here
• [ ] Reviewed against plain language guidelines
• [ ] Design QA passed
• [ ] Code must be self-documenting
• [ ] No local tech debt
• [ ] Documentation updated
• [ ] Architectural Decision Record completed as necessary for significant design choices
• [ ] PR reviewed & approved
• [ ] Source code merged

[danielnaab]

SaxonJS was updated to 2.4 in #366. The current latest is 2.5, which has a breaking bug. See here: https://saxonica.plan.io/issues/5749