How to disable address bar expansion in Mozilla Firefox 77?

With the latest update to Firefox, there is a feature that I would like to disable. When you open a window/tab or place the cursor in into the address bar, it becomes a bit bigger. How can I disable / reset this behavior?

address bar before update

address bar after update

_{Some time ago I asked the same question to Firefox 75 and got an answer with a working solution. But the solution for v75 doesn't work for the v77.}

The edits to about:config that worked for earlier versions of Firefox don't work for version 77, but the same results can be achieved through implementation of a userChrome.css file.

A good tutorial on how to create the file can be found at https://www.userchrome.org/how-create-userchrome-css.html, and the content that you need to place in the file has already been worked up and published at https://raw.githubusercontent.com/WesleyBranton/userChrome.css-Customizations/master/css/remove_megabar.css.

I have performed this modification on Firefox 77 running under user-level rights on Windows 10 Enterprise, and it restored the normal url bar.