fix(examples/simple-chatbot): align declared deps with actual usage

The simple-chatbot example imports `httpx` in main.py but the
declared dependency lists were stale:

- `requirements.txt` listed `requests>=2.31.0` (unused; main.py uses
  httpx). PR #1959 removed `requests` from pyproject.toml in 2026-01
  but never cleaned up requirements.txt.
- `pyproject.toml` did not declare `httpx` despite main.py importing
  it, so a fresh `pip install .` would fail at import time.
- README.MD still listed `requests` and showed Python 3.10 instead
  of 3.10+ (which is what pyproject.toml requires).

Replaces `requests` with `httpx` in both dependency files and the
README, and clarifies the Python version constraint.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: GopalGB

examples/clients/simple-chatbot/README.MD

@@ -4,9 +4,9 @@ This example demonstrates how to integrate the Model Context Protocol (MCP) into
 
 ## Requirements
 
-- Python 3.10
+- Python 3.10+
 - `python-dotenv`
-- `requests`
+- `httpx`
 - `mcp`
 - `uvicorn`
 

examples/clients/simple-chatbot/mcp_simple_chatbot/requirements.txt

@@ -1,4 +1,4 @@
 python-dotenv>=1.0.0
-requests>=2.31.0
+httpx>=0.27.0
 mcp>=1.0.0
 uvicorn>=0.32.1

examples/clients/simple-chatbot/pyproject.toml

@@ -16,6 +16,7 @@ classifiers = [
 ]
 dependencies = [
     "python-dotenv>=1.0.0",
+    "httpx>=0.27.0",
     "mcp",
     "uvicorn>=0.32.1",
 ]