Fix tables in Browser detection using UA (for md)

[teoli2003]

This fixes the tables in Browser detection using the user agent and allows the document to be translated in Markdown.

Besides technical fixes, I removed the fourth column when there was one. It was usually either simple comments or empty cells.

A few of these tables are still large, and I may decide to represent them differently in the future; I'll revisit these when I'll complete them, as they are a bit outdated.

This is part of #7536.

[github-actions]

Preview URLs

• https://pr7817.content.dev.mdn.mozit.cloud/en-US/docs/Web/HTTP/Browser_detection_using_the_user_agent

Flaws

None! 🎉

External URLs

URL: /en-US/docs/Web/HTTP/Browser_detection_using_the_user_agent
Title: Browser detection using the user agent
on GitHub

• https://developer.apple.com/library/safari/documentation/AppleApplications/Reference/SafariWebContent/OptimizingforSafarioniPhone/OptimizingforSafarioniPhone.html (1 time) (Note! This may be a new URL 👀)
• https://developers.google.com/chrome/mobile/docs/user-agent (1 time) (Note! This may be a new URL 👀)
• https://my.opera.com/community/openweb/idopera/ (1 time) (Note! This may be a new URL 👀)

(this comment was updated 2021-08-11 10:08:26.057518)