Fix typos found by running ispell on comments and strings

[PhilMiller]

I was reading through the code and encountered a typo, so I systematically sought to fix them.

Notes

• The code itself spells froud though the name is Froude. I didn't change the variable names (cf https://en.wikipedia.org/wiki/Froude_number)

Checklist

• PR has an informative and human-readable title
• Changes are limited to a single goal (no scope creep)
• Code can be automatically merged (no conflicts)
• Code follows project standards (link if applicable)
• Passes all existing automated tests
• Any change in functionality is tested
• New functions are documented (with a description, list of inputs, and expected output)
• Placeholder code is flagged / future todos are captured in comments
• Visually tested in supported browsers and devices (see checklist below 👇)
• Project documentation has been updated (including the "Unreleased" section of the CHANGELOG)
• Reviewers requested with the Reviewers tool ➡️

[PhilMiller]

Thanks for the review!

I'm not on whichever team owns t-route, so I can't merge this myself.