Fix tests, submit content branch portion

spec/frontend/static_site_editor/mock_data.js

@@ -34,6 +34,9 @@ export const savedContentMeta = {
 };
 
 export const submitChangesError = 'Could not save changes';
+export const commitBranchResponse = {
+  web_url: '/tree/root-master-patch-88195',
+};
 export const commitMultipleResponse = {
   short_id: 'ed899a2f4b5',
   web_url: '/commit/ed899a2f4b5',

spec/frontend/static_site_editor/services/submit_content_changes_spec.js

@@ -13,6 +13,7 @@ import submitContentChanges from '~/static_site_editor/services/submit_content_c
 import {
   username,
   projectId,
+  commitBranchResponse,
   commitMultipleResponse,
   createMergeRequestResponse,
   sourcePath,
@@ -26,7 +27,7 @@ describe('submitContentChanges', () => {
   const branch = 'branch-name';
 
   beforeEach(() => {
-    jest.spyOn(Api, 'createBranch').mockResolvedValue();
+    jest.spyOn(Api, 'createBranch').mockResolvedValue({ data: commitBranchResponse });
     jest.spyOn(Api, 'commitMultiple').mockResolvedValue({ data: commitMultipleResponse });
     jest
       .spyOn(Api, 'createProjectMergeRequest')