Update setup instructions and remove some unused files and instructions

[bbondy]

Summary

The longer term plan seems to be to make skus run in its own command.
However as it stands now in the current state a lot of the setup is broken.
This updates some outdated instructions and removes some unused things to make setup for new devs easier.

Changes include:

• Update minimum Go version
• go get is no longer supported outside a module, update to go install
• Update outdated path for payments in README and remove superfluous redirection character
• Update a couple of outdated paths in the services/skus/README.md file
• Fix some wrong setup instructions in services/skus/README.md
• Removes some unused commands from the Makefile and from the READMEs.

Type of Change

• Product feature
• Bug fix
• Performance improvement
• Refactor
• Other

Tested Environments

• Development
• Staging
• Production

Before Requesting Review

• Have documented new functionality in README or in comments?
• Have you squashed all intermediate commits?
• Is there a clear title that explains what the PR does?
• Have you performed a self review of this PR?

Not applicable:

• Does your code build cleanly without any errors or warnings?
• Have you used auto closing keywords?
• Have you added tests for new functionality?
• Have validated query efficiency for new database queries?
• Have you used intuitive function, variable and other naming?
• Have you requested security and/or privacy review if needed

Manual Test Plan

[clD11]

LGTM approved.