Fix code generation (#2545)

Python 3.8 does not support the new syntax used in utils/run-unasync.py,
but using Python 3.12 failed because tokenization of f-strings changed
in Python 3.12 in a way that was not supported by unasync 0.5.0.

Author: pquentin

.buildkite/Dockerfile

@@ -1,4 +1,4 @@
-ARG PYTHON_VERSION=3.8
+ARG PYTHON_VERSION=3.12
 FROM python:${PYTHON_VERSION}
 
 # Default UID/GID to 1000

noxfile.py

@@ -73,7 +73,7 @@ def test_otel(session):
 
 @nox.session()
 def format(session):
-    session.install("black~=24.0", "isort", "flynt", "unasync", "setuptools")
+    session.install("black~=24.0", "isort", "flynt", "unasync>=0.6.0")
 
     session.run("python", "utils/run-unasync.py")
     session.run("isort", "--profile=black", *SOURCE_FILES)