bugfix: rm unexpected errlogger param while calling MCPSessionManager (oneliner)

[n0npax]

Fixes:

_init__
    self._session_manager = MCPSessionManager(
                            ^^^^^^^^^^^^^^^^^^
TypeError: MCPSessionManager.__init__() got an unexpected keyword argument 'errlogger'

with current main: 71bd808 creating an MCP like:

def create_REDACTED_agent():
    """Gets tools from MCP Server."""
    playwright_tools = MCPToolset(
        connection_params=StdioServerParameters(
            command="npx",
            args=[
                "-y",
                "@playwright/mcp@latest",
                #         "--vision"
            ],
        ),
    )
    tools = [playwright_tools, .... redacted]
    redacted_agent = LlmAgent(
      name="redacted_agent",
      model=MODEL,
      tools=tools,
    ...
    return redacted_agent

fails as per:

  File "/Users/redacted/Developer/workspace/redacted/redacted/__init__.py", line 1, in <module>
    from . import agent
  File "/Users/redacted/Developer/workspace/redacted/redacted/agent.py", line 39, in <module>
    redacted_agent = create_redacted_agent()
                  ^^^^^^^^^^^^^^^^^^^^
  File "/Users/redacted/Developer/workspace/redacted/redacted/redacted/agent.py", line 11, in create_redacted_agent
    playwright_tools = MCPToolset(
                       ^^^^^^^^^^^
  File "/Users/redacted/Developer/workspace/redacted/.venv/lib/python3.12/site-packages/google/adk/tools/mcp_tool/mcp_toolset.py", line 89, in __init__
    self._session_manager = MCPSessionManager(
                            ^^^^^^^^^^^^^^^^^^
TypeError: MCPSessionManager.__init__() got an unexpected keyword argument 'errlogger'

and it looks like just orphaned param wasn't properly cleaned up, hence this PR.
you can confirm there is no more occurences of errlogger here: https://github.com/search?q=repo%3Agoogle%2Fadk-python%20errlogger&type=code