Changing require to require_in

As @moreda brought up in a comment on https://github.com/saltstack-formulas/jenkins-formula/commit/18c423f5f5f783bd31225c2d710c382b7d536b62 :

```
 - require:
       - pkgrepo: jenkins
```
won't work as expected because pkgrepo is expected to be used via "require_in" according to http://docs.saltstack.com/en/latest/ref/states/all/salt.states.pkgrepo.html#management-of-apt-yum-package-repos

```
require_in
    Set this to a list of pkg.installed or pkg.latest to trigger the running of apt-get update prior to attempting to install these packages. Setting a require in the pkg will not work for this.
```