I18N of protected_branches directory

This is one of many MRs opened in order to improve the overall
internationalisation of the GitLab codebase.

This commit only targets Vanilla JS files.

i18n documentation
https://docs.gitlab.com/ee/development/i18n/externalization.html

app/assets/javascripts/protected_branches/protected_branch_access_dropdown.js

+import { __ } from '~/locale';
+
 export default class ProtectedBranchAccessDropdown {
   constructor(options) {
     this.options = options;
@@ -15,7 +17,7 @@ export default class ProtectedBranchAccessDropdown {
         if ($el.is('.is-active')) {
           return item.text;
         }
-        return 'Select';
+        return __('Select');
       },
       clicked(options) {
         options.e.preventDefault();

app/assets/javascripts/protected_branches/protected_branch_create.js

@@ -2,6 +2,7 @@ import $ from 'jquery';
 import ProtectedBranchAccessDropdown from './protected_branch_access_dropdown';
 import CreateItemDropdown from '../create_item_dropdown';
 import AccessorUtilities from '../lib/utils/accessor';
+import { __ } from '~/locale';
 
 export default class ProtectedBranchCreate {
   constructor() {
@@ -35,7 +36,7 @@ export default class ProtectedBranchCreate {
 
     this.createItemDropdown = new CreateItemDropdown({
       $dropdown: $protectedBranchDropdown,
-      defaultToggleLabel: 'Protected Branch',
+      defaultToggleLabel: __('Protected Branch'),
       fieldName: 'protected_branch[name]',
       onSelect: this.onSelectCallback,
       getData: ProtectedBranchCreate.getProtectedBranches,

app/assets/javascripts/protected_branches/protected_branch_edit.js

 import flash from '../flash';
 import axios from '../lib/utils/axios_utils';
 import ProtectedBranchAccessDropdown from './protected_branch_access_dropdown';
+import { __ } from '~/locale';
 
 export default class ProtectedBranchEdit {
   constructor(options) {
@@ -68,7 +69,7 @@ export default class ProtectedBranchEdit {
         this.$allowedToPushDropdown.enable();
 
         flash(
-          'Failed to update branch!',
+          __('Failed to update branch!'),
           'alert',
           document.querySelector('.js-protected-branches-list'),
         );

locale/gitlab.pot

@@ -5030,6 +5030,9 @@ msgstr ""
 msgid "Failed to signing using smartcard authentication"
 msgstr ""
 
+msgid "Failed to update branch!"
+msgstr ""
+
 msgid "Failed to update issues, please try again."
 msgstr ""
 
@@ -9817,6 +9820,9 @@ msgstr ""
 msgid "Protected"
 msgstr ""
 
+msgid "Protected Branch"
+msgstr ""
+
 msgid "Protected Environments"
 msgstr ""