Autocapitalize further update

[chrisdavidmills]

Summary

We recently made some changes to the autocapitalize content; see mdn/content#30734 (review) for test case, and the changes that were made. This was done before I realized that autocapitalize is a true global attribute - it is also available on any contenteditable element.

This PR removes autocapitalize from the form element, so it is just on global attributes.

My next move will be to update the content again so that all the nice updated details we wrote about autocapitalize will be moved from the form elements they are relevant to, and put on the global attribute page.

Test results and supporting details

Related issues

[teoli2003]

👍 Feel free to ping me on slack once the content update PR is ready, so it can get a prompt merge (As you already reviewed the original PR and I read part of it this morning, too)