Ensure the ngettext (JS) util emulates the Django global if not present

Follow up from #9617

client/src/utils/gettext.test.js

@@ -30,8 +30,9 @@ describe('gettext', () => {
 });
 
 describe('ngettext', () => {
-  it('should return the first param if Django ngettext is not loaded', () => {
-    expect(ngettext('One bird', 'Many birds', 2)).toEqual('One bird');
+  it('should emulate the Django ngettext function if it is not loaded', () => {
+    expect(ngettext('One bird', 'Many birds', 1)).toEqual('One bird');
+    expect(ngettext('One bird', 'Many birds', 2)).toEqual('Many birds');
   });
 
   it('should call the global Django util if loaded', () => {

client/src/utils/gettext.ts

@@ -48,7 +48,7 @@ export function ngettext(
     return djangoNgettext(singular, plural, count);
   }
 
-  return singular;
+  return count === 1 ? singular : plural;
 }
 
 /**