Please note that you may end up with an "View Pocket List" entry in the bookmarks menu when you disable Pocket this way.

If you want to get rid of the bookmarks menu entry as well, you need to handle things slightly different.

1) Make sure Pocket is enabled in Firefox (browser.pocket.enabled is set to true). The icon should show up in the main Firefox toolbar.

2) Click on the Hamburger menu icon and select customize from the options.

3) Drag and drop the Pocket icon away from the toolbar so that it is not visible anymore.

4) This hides the bookmarks menu entry as well.