Cleanup unused code in pipelines/index.js file

app/assets/javascripts/pages/projects/pipelines/new/index.js

-import $ from 'jquery';
-import setupNativeFormVariableList from '~/ci_variable_list/native_form_variable_list';
-import NewBranchForm from '~/new_branch_form';
-import initNewPipeline from '~/pipeline_new/index';
+import initNewPipelineForm from '~/pipeline_new/index';
 
-const el = document.getElementById('js-new-pipeline');
-
-if (el) {
-  initNewPipeline();
-} else {
-  new NewBranchForm($('.js-new-pipeline-form')); // eslint-disable-line no-new
-
-  setupNativeFormVariableList({
-    container: $('.js-ci-variable-list-section'),
-    formField: 'variables_attributes',
-  });
-}
+initNewPipelineForm();