Fix PHP 7.4 compatibility warnings in Homebox

Problem/Motivation

When running PHPCompatibility against Homebox, you get the following warning:

sites/all/modules/contrib/homebox/homebox.features.inc
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FOUND 0 ERRORS AND 1 WARNING AFFECTING 1 LINE
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 75 | WARNING | Passing the $glue and $pieces parameters in reverse order to
    |         | implode has been deprecated since PHP 7.4; $glue should be the
    |         | first parameter and $pieces the second
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Proposed resolution

Fix it.

Remaining tasks

Do it.

User interface changes

API changes

Data model changes

Release notes snippet