Eliminate calls to flattenSingleValue() that are no longer required w…

[MarkBaker]

Eliminate calls to flattenSingleValue() that are no longer required when we're checking for array values as arguments

This is:

- [ ] a bugfix
- [ ] a new feature
- [X] refactoring

Checklist:

• Changes are covered by unit tests
• Code style is respected
• Commit message explains why the change is made (see https://github.com/erlang/otp/wiki/Writing-good-commit-messages)
• CHANGELOG.md contains a short summary of the change
• Documentation is updated as necessary

Why this change is needed?

array argument checking eliminates the need for flattening those arguments by calling flattenSingleValue() because the array argument handling inside the ArrayEnabled Trait already flattens those arguments