feat: allow sls v4

[astuyve]

What does this PR do?

Closes #493, allows sls v4

Motivation

I had some time to smoke test it and everything seems to work okay. It does not seem like v4 has changed much in terms of functionality because the cloudformation template is still valid and the plugin managed to redirect handlers and apply the correct instrumentation.

So I believe opening up this restriction is safe.

Testing Guidelines

Additional Notes

Types of changes

• [ ] Bug fix
• [ ] New feature
• [ ] Breaking change
• [ ] Misc (docs, refactoring, dependency upgrade, etc.)

Check all that apply

• [ ] This PR's description is comprehensive
• [ ] This PR contains breaking changes that are documented in the description
• [ ] This PR introduces new APIs or parameters that are documented and unlikely to change in the foreseeable future
• [ ] This PR impacts documentation, and it has been updated (or a ticket has been logged)
• [ ] This PR's changes are covered by the automated tests
• [ ] This PR collects user input/sensitive content into Datadog