build(deps): bump ruff from 0.15.12 to 0.15.15

Bumps [ruff](https://github.com/astral-sh/ruff) from 0.15.12 to 0.15.15.
- [Release notes](https://github.com/astral-sh/ruff/releases)
- [Changelog](https://github.com/astral-sh/ruff/blob/main/CHANGELOG.md)
- [Commits](astral-sh/ruff@0.15.12...0.15.15)

---
updated-dependencies:
- dependency-name: ruff
  dependency-version: 0.15.15
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

requirements.txt

@@ -1,3 +1,3 @@
 pytest==9.0.3
-ruff==0.15.12
+ruff==0.15.15
 slack-bolt==1.28.0