ownCloud Web: support browsers that are 1 year old

[mmattel]

WHAT Needs to be Documented?

With the next stable release, the supported browser list / version needs an update.

References: owncloud/web#8135 (feat: support browsers that are 1 year old)

WHERE Does This Need To Be Documented (Link)?

https://doc.owncloud.com/webui/next/owncloud_web/requirements.html#desktop-requirements

WHY Should This Change Be Made?

Update the supported browser list.

(Optional) What Type Of Content Change Is This?

• New Content Addition
• Old Content Deprecation
• Existing Content Simplification
• Bug Fix to Existing Content