Correct the playbook in doc for revocation example

[mrizwan93]

playbook mentioned at https://github.com/freeipa/ansible-freeipa/blob/master/README-cert.md

---
- name: Revoke certificate
  hosts: ipaserver

  tasks:
  - name Revoke a certificate
    ipacert:
      ipaadmin_password: SomeADMINpassword
      serial_number: 123456789
      state: revoked

It doesn't state the revocation reason. Also colon is missing in name directive of tasks Correct example playbook would be:

---
- name: Revoke certificate
  hosts: ipaserver

  tasks:
  - name: Revoke a certificate
    ipacert:
      ipaadmin_password: SomeADMINpassword
      serial_number: 123456789
      reason: 5
      state: revoked

[rjeffman]

@mrizwan93 thank you for the report!