replace iteritems for python3

Details: https://github.com/saltstack/salt/issues/47461

iteritems is only in python2 thing, when using python3 you cannot use iteritems, you use just items() which returns a generator in python3, like iteritems did in python2.

root@salt:/home/skorpy# salt 'prometheus*' state.apply                                                                                                                                                                                                                         │·
prometheus1.aixit.off.de.ffffm.net:                                                                                                                                                                                                                                            │·
    Data failed to compile:                                                                                                                                                                                                                                                    │·
----------                                                                                                                                                                                                                                                                     │·
    Rendering SLS 'base:letsencrypt' failed: Jinja variable 'dict object' has no attribute 'iteritems'                                                                                                                                                                         │·
----------                                                                                                                                                                                                                                                                     │·
    Rendering SLS 'base:nginx.vhosts' failed: Jinja variable 'dict object' has no attribute 'iteritems'                                                                                                                                                                        │·
ERROR: Minions returned with non-zero exit code                                                                                                                                                                                                                                │·
root@salt:/home/skorpy# salt 'www3.aixit.*' state.apply                                                                                                                                                                                                                        │·
www3.aixit.off.de.ffffm.net:                                                                                                                                                                                                                                                   │·
    Data failed to compile:                                                                                                                                                                                                                                                    │·
----------                                                                                                                                                                                                                                                                     │·
    Rendering SLS 'base:nginx.vhosts' failed: Jinja variable 'dict object' has no attribute 'iteritems'                                                                                                                                                                        │·
----------                                                                                                                                                                                                                                                                     │·
    Rendering SLS 'base:letsencrypt' failed: Jinja variable 'dict object' has no attribute 'iteritems'                                                                                                                                                                         │·
ERROR: Minions returned with non-zero exit code