[FIX] hr_holidays: subscription and emails

[FIX] auto subscription

- removed auto subscription of managers for leave / allocation requests as this
  can be managed through subscripion to the department
- updated some subtype labels
- removed auto subscription of leave / allocation creator as the employee is already
  automatically subscribed; managers creating leave and allocation in batch should
  not automatically follow the created records except through the department
  subscription

[FIX] notification email batch

- add a context key to use the email queue for notifications linked
  to allocations created in batch
- also fixed a missing context in a browse