Honestly you are better off removing everything from your robots.txt. As far as I can see, all PHP files in Joomla contain the line

defined('_JEXEC') or die;

Which means if you load a PHP file directly in the browser all you get is a blank file, which search engines will ignore. (They shouldn't ever come across these anyway unless you linked them directly.)

The problem with leaving some of this directories blocked is that some components and modules keep their CSS/JS files inside those respective directories and not in the preferred media or images folders.

So there is no reason to block any Joomla files from Google.

Honestly you are better off removing everything from your robots.txt. As far as I can see, all PHP files in Joomla contain the line

defined('_JEXEC') or die;

Which means if you load a PHP file directly in the browser all you get is a blank file, which search engines will ignore. (They shouldn't ever come across these anyway unless you linked them directly.)

The problem with leaving some of these directories blocked is that some components and modules keep their CSS/JS files inside those respective directories and not in the preferred media or images folders.

So there is no reason to block any Joomla files from Google.