build(deps): bump ruff from 0.15.19 to 0.15.20 (#131)

Bumps [ruff](https://github.com/astral-sh/ruff) from 0.15.19 to 0.15.20.
- [Release notes](https://github.com/astral-sh/ruff/releases)
- [Changelog](https://github.com/astral-sh/ruff/blob/main/CHANGELOG.md)
- [Commits](astral-sh/ruff@0.15.19...0.15.20)

---
updated-dependencies:
- dependency-name: ruff
  dependency-version: 0.15.20
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

claude-agent-sdk/requirements.txt

@@ -7,4 +7,4 @@ python-dotenv==1.2.2
 
 pytest==9.1.1
 pytest-asyncio==1.4.0
-ruff==0.15.19
+ruff==0.15.20

openai-agents-sdk/requirements.txt

@@ -5,4 +5,4 @@ openai-agents==0.17.7
 python-dotenv==1.2.2
 
 pytest==9.1.1
-ruff==0.15.19
+ruff==0.15.20

pydantic-ai/requirements.txt

@@ -5,4 +5,4 @@ pydantic-ai[openai,anthropic]==1.107.0
 python-dotenv==1.2.2
 
 pytest==9.1.1
-ruff==0.15.19
+ruff==0.15.20