Doc revisions arising from running through the Support GET training module

What does this MR do?

Improvements to the documentation for initial setup of GET

Some of my suggestions are probably considered to assumed by the statement:

This quick guide [..] assumes a good working knowledge of Terraform, Ansible and GitLab

However, there's a number of audiences for this documentation and solution, including the Support Team, who cannot be assumed to have a good working knowledge of Terraform and Ansible. I anticipate we'll increasingly get support tickets from customers in the same position - like we do with cloud native deployments 😉

Related issues

gitlab-com/support/support-training#3379 (closed) https://gitlab.com/gitlab-org/quality/quality-enablement-issue-tracker/-/issues/25

Author's checklist

When ready for review, the Author applies the workflowready for review label and mention @gl-quality/get-maintainers:

• Merge request:
  • Corresponding Issue raised and reviewed by the GET maintainers team.
  • Merge Request Title and Description are up-to-date, accurate, and descriptive
  • MR targeting the appropriate branch
  • MR has a green pipeline
  • MR has no new security alerts in the widget from the Secret Detection and IaC Scan (SAST) jobs.
• Code:
  • Check the area changed works as expected. Consider testing it in different environment sizes (1k,3k,10k,etc.).
  • Documentation created/updated in the same MR.
  • If this MR adds an optional configuration - check that all permutations continue to work.
  • For Terraform changes: set up a previous version environment, then run a terraform plan with your new changes and ensure nothing will be destroyed. If anything will be destroyed and this can't be avoided please add a comment to the current MR.
• Create any follow-up issue(s) to support the new feature across other supported cloud providers or advanced configurations. Create 1 issue for each provider/configuration. Contact the Quality Enablement team if unsure.