Removing unused prop type in StreamRuleList component. (#2673)

There was an unused prop type defined in the StreamRuleList component,
which was not passed to it, therefore generating a warning in the
browser's console for every use of the component. This change removes
the prop type.

graylog2-web-interface/src/components/streamrules/StreamRuleList.jsx

@@ -10,7 +10,6 @@ const StreamRuleList = React.createClass({
     onDelete: React.PropTypes.func,
     permissions: React.PropTypes.array.isRequired,
     stream: React.PropTypes.object.isRequired,
-    streamRule: React.PropTypes.object.isRequired,
     streamRuleTypes: React.PropTypes.array.isRequired,
   },