docs: Removes unnecessary content from tutorial

[gruyaume]

Description

The different subheadings that were in the tutorial aren't necessary as they contain the same content as the following sentence (example below). This PR removed those unnecessary subheaders. This PR also removes the unnecessaty "juju switch" command since we only need 1 model now.

Before:

### Install MicroK8s

From your terminal, install MicroK8s:

After:

From your terminal, install MicroK8s:

Checklist:

• [ ] My code follows the style guidelines of this project
• [ ] I have performed a self-review of my own code
• [ ] I have made corresponding changes to the documentation
• [ ] I have added tests that validate the behaviour of the software
• [ ] I validated that new and existing unit tests pass locally with my changes
• [ ] Any dependent changes have been merged and published in downstream modules
• [ ] I have bumped the version of the library