Add mcp dependency to google-adk extra - #1736

What was changed

Added mcp>=1.24,<2 to the google-adk extra (plus uv.lock and a CHANGELOG entry under Fixed).

Why

A fresh pip install temporalio[google-adk] could not import the contrib package:

File ".../google_adk_agents/_mcp.py", line 13, in <module>
    from google.adk.tools.mcp_tool import McpToolset
ImportError: cannot import name 'McpToolset' from 'google.adk.tools.mcp_tool'

google-adk only exports McpToolset when the optional mcp package is importable and keeps mcp behind its own extra, which ours didn't pull in. The constraint matches google-adk's own mcp extra across our supported range (2.2.0–current), following the precedent of our openai-agents extra.

How was this tested

Fresh-venv before/after with only the google-adk extra: reproduces the ImportError on main's metadata, imports cleanly with this change. uv lock --check, poe lint, and pytest tests/contrib/google_adk_agents (39 passed, 5 skipped) all pass.