feat(php): add rubocop linter to pre-commit

`rubocop` already fixed during the previous PR:

* saltstack-formulas/php-formula#221

Author: myii

ssf/formulas.yaml

@@ -3643,7 +3643,6 @@ ssf:
           - [fedora       ,   30   ,   2018.3,      3,       redhat]
           - [opensuse/leap,   15.1 ,   2018.3,      2,         suse]
           # # - [centos       ,    6   ,   2017.7,      2,       redhat]
-        travis: *travis_do_not_use_single_job_for_linters
         use_tofs: true
       semrel_files: *semrel_files_inc_map_jinja_verifier
     postfix: