Bump test/fixtures/prism from b3cef9d to 2b60deb

Bumps [test/fixtures/prism](https://github.com/ruby/prism) from `b3cef9d` to `2b60deb`.
- [Release notes](https://github.com/ruby/prism/releases)
- [Commits](ruby/prism@b3cef9d...2b60deb)

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

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]