Cleanup 3 LookupRef Tests

[oleibman]

Scrutinizer had previously suggested annotations for 3 LookupRef tests, but it no longer accepts its own annotation for those cases. This PR cleans them up. ColumnsTest and RowsTest are extremely straightforward.

IndexTest is a bit more complicated, but only because, unlike the other two, it had no test which executed in the context of a spreadsheet. And, when I added those, I discovered a couple of bugs. INDEX always requires at least 2 parameters (row# is always required), but its entry in the function table specified 1-4 parameters, now changed to 2-4. And, omitting col# is not handled the same way as specifying 0 for col#, though the code had treated them identically. (The same would have been true for row# but, because it is now required, ...)

This is:

- [x] a bugfix
- [ ] a new feature
- [ ] refactoring
- [ ] additional unit tests

Checklist:

• Changes are covered by unit tests
  • Changes are covered by existing unit tests
  • New unit tests have been added
• 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?

Provide an explanation of why this change is needed, with links to any Issues (if appropriate).
If this is a bugfix or a new feature, and there are no existing Issues, then please also create an issue that will make it easier to track progress with this PR.