Bump test/fixtures/prism from 2e9bf5e to bac76e8

Bumps [test/fixtures/prism](https://github.com/ruby/prism) from `2e9bf5e` to `bac76e8`.
- [Release notes](https://github.com/ruby/prism/releases)
- [Commits](ruby/prism@2e9bf5e...bac76e8)

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

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