Bump src/main/resources/csl-styles from b90b81a to 6b7b611 (#12254)

Bumps [src/main/resources/csl-styles](https://github.com/citation-style-language/styles) from `b90b81a` to `6b7b611`.
- [Release notes](https://github.com/citation-style-language/styles/releases)
- [Commits](citation-style-language/styles@b90b81a...6b7b611)

---
updated-dependencies:
- dependency-name: src/main/resources/csl-styles
  dependency-type: direct:production
...

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