Mock the correct `external_email` method.

spec/lib/gitlab/ldap/access_spec.rb

@@ -8,7 +8,7 @@ describe Gitlab::LDAP::Access, lib: true do
   describe '#find_ldap_user' do
     it 'finds a user by dn first' do
       expect(Gitlab::LDAP::Person).to receive(:find_by_dn).and_return(:ldap_user)
-      expect(user).not_to receive(:ldap_email?)
+      expect(user).not_to receive(:external_email?)
 
       access.find_ldap_user
     end