Linter: Improve erb-no-instance-variables-in-partials offense message

[marcoroth]

This pull request updates the offense messages of erb-no-instance-variables-in-partials to name the concrete local variable that should be used instead of the instance variable.

- Avoid using instance variables in partials. Pass `@talks` as a local variable instead.
+ Avoid using instance variables in partials. Use the local variable `talks` instead of `@talks` and pass it in via `locals`.

- Avoid setting instance variables in partials. Use a local variable instead of `@talks`.
+ Avoid setting instance variables in partials. Assign the local variable `talks` instead of `@talks`.

[github-actions]

🌿 Interactive Playground and Documentation Preview

A preview deployment has been built for this pull request. Try out the changes live in the interactive playground:

• Playground Preview
• Documentation Preview
• Website Preview

---

_{🌱 Grown from commit 4c24961}

---

✅ Preview deployment has been cleaned up.

[pkg-pr-new]

npx https://pkg.pr.new/@herb-tools/formatter@2046

npx https://pkg.pr.new/@herb-tools/language-server@2046

npx https://pkg.pr.new/@herb-tools/linter@2046

commit: 4c24961