chore: remove requirements.txt in favour of pyproject.toml for claude-agent-sdk

Co-Authored-By: Claude <svc-devxp-claude@slack-corp.com>

Author: zimeg

claude-agent-sdk/README.md

@@ -140,7 +140,7 @@ source .venv/bin/activate  # for Windows OS, .\.venv\Scripts\Activate instead sh
 #### Install dependencies
 
 ```sh
-pip install -r requirements.txt
+pip install -e ".[dev]"
 ```
 
 ## Providers