This is already the version which will be available for next i-MSCP maintenance version.
Can we just overwrite the files with the files from the archive?
You can as long as you known what you're doing. You should just save and restore the config file and set the gui permissions once done: perl /var/www/imscp/engine/setup/set-gui-permissions.pl -dv
Note that the PhpMyAdmin 4.8.5 version will be available in next maintenance release.