Add enum API version 2021-10

[romainbriand]

WHY are these changes introduced?

Enum for the "2021-10" API version is missing in the package.

WHAT is this pull request doing?

It adds a new enum for the "2021-10" API version.

Type of change

• Patch: Bug (non-breaking change which fixes an issue)
• Minor: New feature (non-breaking change which adds functionality)
• Major: Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist

• I have added a changelog entry, prefixed by the type of change noted above
• I have added/updated tests for this change
• I have documented new APIs/updated the documentation for modified APIs (for public APIs)

[mllemango]

Thanks! We'll package this up and release it as a patch soon :)