build(deps): bump ruff from 0.15.15 to 0.15.20 (#82)

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

requirements.txt

@@ -1,3 +1,3 @@
 slack-bolt==1.28.0
 pytest==9.1.1
-ruff==0.15.15
+ruff==0.15.20