PHP 8 incompatibility in subscriptions.module: implode parameter order

Problem/Motivation

phpcs, checking PHP 8.1 compatibility, reports this for subscriptions 7.x-1.4:

FILE: subscriptions/subscriptions.module
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FOUND 1 ERROR AFFECTING 1 LINE
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 819 | ERROR | Passing the $glue and $pieces parameters in reverse order to implode has been deprecated since PHP 7.4 and is removed since PHP 8.0; $glue should be the first parameter and $pieces the
     |       | second
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Steps to reproduce

Run phpcs PHPCompatibility scan for PHP version 8.1 .

Proposed resolution

Amend line 819 of subscriptions.module to correct the order of parameters to implode().