Bump test/fixtures/prism from d290a34 to 67c1b31

Bumps [test/fixtures/prism](https://github.com/ruby/prism) from `d290a34` to `67c1b31`.
- [Release notes](https://github.com/ruby/prism/releases)
- [Commits](ruby/prism@d290a34...67c1b31)

---
updated-dependencies:
- dependency-name: test/fixtures/prism
  dependency-version: 67c1b31641ffcf4b8778314e1644bb9317a5bc62
  dependency-type: direct:production
...

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Author: dependabot[bot]