Correct default http_version from float to string

[downingar]

Proposed changes

This is a simple fix that corrects the value of the default http_version to a string, which is what is required/expected by Nginx itself.

Checklist

Before creating a PR, run through this checklist and mark each as complete:

• [x] I have read the CONTRIBUTING document.
• [ ] I have added Molecule tests that prove my fix is effective or that my feature works.
• [ ] I have checked that any relevant Molecule tests pass after adding my changes.
• [ ] I have updated any relevant documentation (defaults/main/*.yml, README.md and CHANGELOG.md).

I'll admit to being lazy and not running any Molecule tests here, though one should probably be added to catch this. I have very little experience with Molecule, but I'm willing to add it if someone can give me a few hints on where to look and what to do.