refactor: tweak two phrase set corrections

[hippietrail]

Issues

N/A

Description

While looking into a new phrase set correction I noticed two ones I recently added that weren't quite right. Both just had single corrections rather than sets.

• One, InHindsight was moved to a Weir rule.
• The other, ArgumentToBeMade was extended to cover plural as well as singular.

How Has This Been Tested?

cargo test

AI Disclosure

• I am a human and didn't use any AI.
• I used LLM features of my editor, but not an agent.
• I used an AI agent interactively.
• I am an agent or I got an agent to do the work autonomously.

If Your PR Implements or Enhances a Linter

• I made up the sentences in the unit tests.
• The sentences in the unit tests were generated by an AI.
• I'm using examples from the bug report / feature request.
• I collected real-world sentences for the unit tests.

Checklist

• I have performed a self-review of my own code
• I have added tests to cover my changes
• I have considered splitting this into smaller pull requests.