Improve the "Deploying" section of the docs

[noahtalerman]

This issue corresponds to the following Product goal in the Q2 OKRs:

Submit pull request once a week to consolidate documentation updates in partnership with Customer Engineering

Goal

As a Fleet user landing on the Introduction page in the Deployment docs, I want instructions and code samples on how to deploy Fleet to be the first thing I see.

Tasks

• On, the Introduction page, bring AWS Terraform instructions to the top fold
  • The top fold should explain the minimum steps to be successful with deploying Fleet with Terraform
  • The top fold should also include the commands to run the Terraform code.
• Bring the Render and Kubernetes instructions below the top fold on the Introduction page.
• Remove the "Server Installation" page. This includes removing the "CentOS, Ubuntu, Docker, and Community projects sections.