Update Postgres Datediff

There was a problem when using:
$query -> func() -> dateDiff( [ 'COALESCE(Articles.modified, Articles.created)' => 'literal', date( "Y-m-d H:i:s" ) ] )
Code format
Remove ABS
Add space (formatting)
Fix formatting
Merge pull request #4941 from Laykou/patch-2

Update Postgres Datediff