Remove unused (and broken) helper group declaration.

The 'universal_variable_data_helper' helper group is not needed and not setup properly. Trying to call Mage::helper('universal_variable_data_helper') results in a fatal error:

Fatal error: Uncaught exception 'Exception' with message 'Warning: include(QuBit/UniversalVariable/Helper/Data/Data.php): failed to open stream: No such file or directory in /mnt/Projects/uv/lib/Varien/Autoload.php on line 93' in /mnt/Projects/uv/app/code/core/Mage/Core/functions.php on line 245


Also cleaned up tabs from <helper> node.