Remove unnecessary IIFE from build_spec

spec/javascripts/build_spec.js.es6

@@ -9,8 +9,7 @@
 //= require jquery.nicescroll
 //= require turbolinks
 
-(() => {
-  describe('Build', () => {
+describe('Build', () => {
   // see spec/factories/ci/builds.rb
   const BUILD_TRACE = 'BUILD TRACE';
   // see lib/ci/ansi2html.rb
@@ -187,5 +186,4 @@
       });
     });
   });
-  });
-})();
+});