Update README.md to remove /tmp

[cybertech99]

In a Wells Fargo class hosted by RedHat I discovered this doc was using /tmp/backup which is not correct. The backup folder is in the root.

Removed all references of /tmp/backup to /backup

SUMMARY

ISSUE TYPE

• Bugfix Pull Request
• Docs Pull Request
• Feature Pull Request

COMPONENT NAME

• exercises
• docs
• decks
• provisioner
• demos

ADDITIONAL INFORMATION

[IPvSean]

Three quick points !

• I really appreciate the PR! Thank you for taking the time to make it.
• I already fixed this from a bug issue here: https://github.com/IPvSean/workshops/tree/gh-pages/exercises/ansible_network/6-tower-job-template . But I have not done a PR yet... I am sorry in this delay... this would have saved you time. I did document this in the issue here:Network Exercise 6, Step 5 #399 but that could easily be missed.
• I would just accept this PR regardless, but you need to submit to the devel branch and not master this is outlined here in the contribute guide: https://github.com/ansible/workshops/blob/master/docs/contribute.md . Submitting to master will cause problems, we only do PRs to master from devel to keep those two branches in sync. This is the release process for Ansible/workshops

Anyways please re-submit to devel or just wait until tomorrow and my PR will go in and make the identical change!