Delete old getting_started doc

Summary

After discussing it with Chris, this information is better provided elsewhere in the repo and this only serves as a possible distraction from where we're trying to route people.

Agree that all this can be safely deleted. There is one part that should be captured in a document.

## System Requirements
- Admin tools
  - [Docker](https://docs.docker.com/engine/install/)
  - [Git](https://git-scm.com/download/)
  - [Helm](https://helm.sh/docs/intro/install/)
  - [Kubectl](https://kubernetes.io/docs/tasks/tools/install-kubectl/)
  - [Kustomize](https://kubectl.docs.kubernetes.io/installation/kustomize/)
  - [SOPS](https://github.com/mozilla/sops/releases)

^-- This snippet should become it's own md file of recommended tools for an admin to install on their machine to help manage a cluster. But again it's safe to delete this b/c another spot in docs has this content documented in a better way.
https://repo1.dso.mil/platform-one/onboarding/big-bang/engineering-cohort/-/blob/master/lab_guides/01-Preflight-Access-Checks/A-software-check.md

@david.allen
I'm 100% good with this being deleted, but I do think this type of info would be good to put back. What are your thoughts about creating a separate ticket to prioritize upstreaming this snippet of bb engineering cohort docs into an upstream repo doc? (slightly higher priority doc, as in this should be added before some of the other cleanup work occurs, just my opinion, feel free to prioritize whichever makes sense to you, but originally I had large chunk of cohort stuff slated for much later but I think this tiny snippet of that larger chunk should maybe be upstreamed sooner is what I'm trying to get at.)
https://repo1.dso.mil/platform-one/onboarding/big-bang/engineering-cohort/-/blob/master/lab_guides/01-Preflight-Access-Checks/A-software-check.md

approved this merge request

I'll make a ticket to track this, thanks!

approved this merge request

merged

mentioned in commit d8186b74