Bump gopkg.in/yaml.v2 to v3 to see if toYaml is better

[iangrunt]

Description

toYaml I don't think formats security/_global/account-baseline/users.yml in a human-readable way, especially with the underscore characters prefixing the strings.

There is no official spec on this, but I think the common formatters will indent two or four spaces before listing elements in a collection:

vs

TODOs

Read the Gruntwork contribution guidelines.

• [ ] Update the docs.
• [x] Run the relevant tests successfully, including pre-commit checks.
• [ ] Ensure any 3rd party code adheres with our license policy or delete this line if its not applicable.
• [ ] Include release notes. If this PR is backward incompatible, include a migration guide.

Release Notes (draft)

Added / Removed / Updated [X].

Migration Guide