PHP8: deprecated code

Problem/Motivation

When upgrading to PHP8, I got this warning:

FILE: hierarchical_select/hierarchical_select.module
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FOUND 0 ERRORS AND 3 WARNINGS AFFECTING 1 LINE
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 1388 | WARNING | Declaring a required parameter after an optional one is deprecated since PHP 8.0. Parameter $dropbox is optional, while parameter $module is required.
 1388 | WARNING | Declaring a required parameter after an optional one is deprecated since PHP 8.0. Parameter $dropbox is optional, while parameter $params is required.
 1388 | WARNING | Declaring a required parameter after an optional one is deprecated since PHP 8.0. Parameter $dropbox is optional, while parameter $save_lineage is required.
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Steps to reproduce

Upgrade server to PHP8, then run a drush command and see warning.

Proposed resolution

Update parameters in function declaration.