Enable and fix RSpec/DescribedClassModuleWrapping

[dduugg]

• Have you followed the guidelines in our Contributing document?
• Have you checked to ensure there aren't other open Pull Requests for the same change?
• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes? Here's an example.
• Have you successfully run brew style with your changes locally?
• Have you successfully run brew typecheck with your changes locally?
• Have you successfully run brew tests with your changes locally?

---

When porting the dev cmds to use the AbstractCommand interface, I noticed that audit_spec contained tests for classes defined in other files, namely FormulaAuditor and FormulaTextAuditor. I've moved those to separate files, according to our usual conventions. I also flipped on RSpec/DescribedClassModuleWrapping and resolved the corresponding violations, which makes this pattern less likely to recur (bc we also don't allow multiple top-level describe blocks in files).

I've also enabled RSpec/FilePath at SpecSuffixOnly, although there were no violations (it requires spec file names to end with _spec.