remove task updating apt cache on every execution

[pescobar]

The role is not idempotent because of this task that is executed on every run

Removing this task should make the role idempotent and should not affect the current behavior as the cache is anyway updated in the task installing the package in https://github.com/OSC/ood-ansible/blob/master/tasks/install-package.yml#L97

[johrstrom]

Looks like the CI is broken. I'm OK with this change, but it looks like I'll need to fix the CI before merging.