Upgrade isort version in pre-commit (encode#8882)

This fixes recent issues with installing isort via pre-commit that was
introduced in recent versions of poetry-core.

See PyCQA/isort#2078

Author: jalaziz

.pre-commit-config.yaml

@@ -9,7 +9,7 @@ repos:
   - id: check-symlinks
   - id: check-toml
 - repo: https://github.com/pycqa/isort
-  rev: 5.8.0
+  rev: 5.12.0
   hooks:
   - id: isort
 - repo: https://github.com/PyCQA/flake8