chore(deps): update dependency isort to v6 (#258)

Author: renovate-bot

pyproject.toml

@@ -40,7 +40,7 @@ Changelog = "https://github.com/googleapis/langchain-google-cloud-sql-pg-python/
 [project.optional-dependencies]
 test = [
     "black[jupyter]==25.1.0",
-    "isort==5.13.2",
+    "isort==6.0.0",
     "mypy==1.11.2",
     "pytest-asyncio==0.24.0",
     "pytest==8.3.3",