servo: Merge #10723 - Remove some Emacs & Vim modelines (from edunham:modelines); r=Wafflespeanut

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

servo/components/script/dom/webidls/Event.webidl

@@ -1,4 +1,3 @@
-/* -*- Mode: IDL; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */