Remove outdated info from project page

Problem/Motivation

The project page says:

Avoid losing content by accident: If a user is editing content and attempts to leave the edit form without first saving it (e.g., closing the browser window/tab, clicking on a link, etc.), they will be notified. If the user confirms that they want to leave without saving the node, the edit lock gets automatically removed by an ajax call. This behaviour can be disabled on the modules settings page.

I don't believe this is true anymore. I believe this is describing something that was available in the D7 version: #2860957: Add D7 functionality for javascript popup when user browses away from page to D8 version

Proposed resolution

Update the documentation.

Remaining tasks

Implement.

User interface changes

None.

API changes

None.

Data model changes

None.