PHP 7.4 deprecated | PHP 8.0 incompatible use of implode()

Problem/Motivation

The current use of implode() in ContentModifyManager.php is deprecated in PHP 7.4 and incompatible with PHP 8.0:

$digest_nodes = $newline . implode($nodes, $newline);

Proposed resolution

Change the call to:

$digest_nodes = $newline . implode($newline, $nodes);