chore(deps): Update ag2[mcp,openai] requirement in /a2a/slack_researcher

Updates the requirements on [ag2[mcp,openai]](https://github.com/ag2ai/ag2) to permit the latest version.
- [Release notes](https://github.com/ag2ai/ag2/releases)
- [Commits](ag2ai/ag2@v0.13.2...v0.14.0)

---
updated-dependencies:
- dependency-name: ag2[mcp,openai]
  dependency-version: 0.14.0
  dependency-type: direct:production
...

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

Author: dependabot[bot]

a2a/slack_researcher/pyproject.toml

@@ -4,7 +4,7 @@ version = "0.1.0"
 requires-python = ">=3.11,<3.13"
 description = "Slack research Agent module"
 dependencies = [
-    "ag2[openai,mcp]>=0.13.2",
+    "ag2[openai,mcp]>=0.14.0",
     "tavily-python>=0.7.26",
     "python-dotenv>=1.2.2",
     "a2a-sdk[http-server]>=1.1.0",