Fix composer rebuild json to remove use of optional modules parameter

Follow-up issue for #2376785: Avoid using moduleHandler for generating the composer.json file.

I do not think the optional module parameter is necessary for the rebuild json drush command anymore because the issue above scans all module directories regardless of installation status.

There is also reference to that modules parameter in ComposerPackages::writeComposerJsonFile() which will call getComposerJsonFiles().