chore: Remove unused tzlocal dependency and logging

The `tzlocal` library and the logging of the local timezone were not used in the `DatabaseSessionService` logic.

Co-authored-by: Liang Wu <wuliang@google.com>
PiperOrigin-RevId: 865677320

Author: wuliang229

src/google/adk/sessions/database_session_service.py

@@ -35,7 +35,6 @@
 from sqlalchemy.ext.asyncio import create_async_engine
 from sqlalchemy.pool import StaticPool
 from typing_extensions import override
-from tzlocal import get_localzone
 
 from . import _session_util
 from ..errors.already_exists_error import AlreadyExistsError
@@ -134,10 +133,6 @@ def __init__(self, db_url: str, **kwargs: Any):
           f"Failed to create database engine for URL '{db_url}'"
       ) from e
 
-    # Get the local timezone
-    local_timezone = get_localzone()
-    logger.info("Local timezone: %s", local_timezone)
-
     self.db_engine: AsyncEngine = db_engine
 
     # DB session factory method