Fix lint errror in ExecuteButton.js

Travis is currently complaining about this ([example build](https://travis-ci.org/graphql/graphiql/builds/181706048)).

Author: wincent

src/components/ExecuteButton.js

@@ -71,7 +71,7 @@ export class ExecuteButton extends React.Component {
 
     const pathJSX = this.props.isRunning ?
       <path d="M 10 10 L 23 10 L 23 23 L 10 23 z" /> :
-        <path d="M 11 9 L 24 16 L 11 23 z" />;
+      <path d="M 11 9 L 24 16 L 11 23 z" />;
 
     return (
       <div className="execute-button-wrap">