Update formatting of code examples (internal)

[geerlingguy]

I just did this for Ansible for Kubernetes, but I want to do it for Ansible for DevOps just to make sure I'm consistent across both books.

I have code examples formatted like so right now:

{lang="text",linenos=off}
    handlers:
      - name: restart apache
        service: name=apache2 state=restarted
    
    tasks:
      - name: Enable Apache rewrite module.
        apache2_module: name=rewrite state=present
        notify: restart apache

But I can use the more simplified method in LeanPub's Markua syntax, allowing easier translation between book text and examples/playbooks:

{lang="text",linenos=off}
```
handlers:
  - name: restart apache
    service: name=apache2 state=restarted

tasks:
  - name: Enable Apache rewrite module.
    apache2_module: name=rewrite state=present
    notify: restart apache
```

Checklist:

• Chapter 1
• Chapter 2
• Chapter 3
• Chapter 4
• Chapter 5
• Chapter 6
• Chapter 7
• Chapter 8
• Chapter 9
• Chapter 10
• Chapter 11
• Chapter 12
• Chapter 13
• Chapter 14
• Appendix A
• Appendix B

[geerlingguy]

(This is just an internal change—ideally it will not result in any reader-facing changes to the text!

[geerlingguy]

I also made sure to update certain config files and such to use proper language highlighting (e.g. use docker highlighting for Dockerfiles). This should make the book's code samples slightly more readable, at least on color screens (probably won't make a difference on the printed copy).