[BUG] cron.present duplicates entries when changing timespec to special

[asomers]

Description
When you change the time specification in a cron.present entry from regular to special or vice versa, it will add the new job but not remove the old one. That results in two jobs with the same name,identifier, and user but different timespecs.

Setup
Please be as specific as possible and give set-up details.

• on-prem machine
• VM (Virtualbox, KVM, etc. please specify)
• VM running on a cloud service, please be explicit and add details
• container (Kubernetes, Docker, containerd, etc. please specify)
• or a combination, please be explicit
• jails if it is FreeBSD

Steps to Reproduce the behavior
Create a state like this in Pillar:

pwd:
  cron.present:
    - identifier: foo

apply state, then change the pillar to this:

pwd:
  cron.present:
    - identifier: foo
    - special: '@hourly'

Apply state again. There will now be two cron jobs in the crontab, that look like this:

Lines below here are managed by Salt, do not edit
# SALT_CRON_IDENTIFIER: foo
* * * * * pwd
# SALT_CRON_IDENTIFIER: foo
@hourly pwd

Expected behavior
cron.present should delete the old * * * * * pwd entry when it creates the new @hourly pwd one.

Versions Report

salt --versions-report

(Provided by running salt --versions-report. Please also mention any differences in master/minion versions.)

Salt Version:
          Salt: 3003.3
 
Dependency Versions:
          cffi: 1.14.6
      cherrypy: Not Installed
      dateutil: 2.8.1
     docker-py: Not Installed
         gitdb: 4.0.7
     gitpython: 3.1.20
        Jinja2: 3.0.0
       libgit2: Not Installed
      M2Crypto: Not Installed
          Mako: Not Installed
       msgpack: 1.0.2
  msgpack-pure: Not Installed
  mysql-python: Not Installed
     pycparser: 2.20
      pycrypto: Not Installed
  pycryptodome: 3.10.1
        pygit2: Not Installed
        Python: 3.8.12 (default, Sep 13 2021, 18:37:45)
  python-gnupg: Not Installed
        PyYAML: 5.4.1
         PyZMQ: 22.2.1
         smmap: 4.0.0
       timelib: Not Installed
       Tornado: 4.5.3
           ZMQ: 4.3.4
 
System Versions:
          dist: freebsd 13.0 
        locale: utf-8
       machine: amd64
       release: 13.0-AXCIENT2
        system: FreeBSD
       version: FreeBSD 13.0</summary>