Remove cruft from context_contrib

As far as I can tell, there is some cruft in context_contrib.module.

Lines 55-62:

/**
 * Implementation of hook_context_reaction().
 */
function context_contrib_context_reaction($context) {
  if (module_exists('css_injector')) {
    _context_contrib_css_injector_response($context);
  }
}

I don't see a hook_context_reaction() being called anywhere, and the function _context_contrib_css_injector_response() doesn't exist as far as I can tell.