This might be a bad idea, especially on the webidl side. However, we started talking about the idea that modelines are a lint error (https://github.com/servo/servo/issues/10719), and these changes would be required before enabling a modeline lint.
If it bitrots, it's easy to recreate with
```
find * -type f -exec sed '/- Mode:/d' -i {} +
find * -type f -exec sed '/ vim:/d' -i {} +
git checkout -- python/tidy/servo_tidy/tidy.py
git checkout -- python/tidy/servo_tidy_tests/spec.webidl
git commit -a
```
Source-Repo: https://github.com/servo/servo
Source-Revision: dff217c2e3ff0b77eeebf62d36c2bf57c044cf14
