Bump optree minimum version

Author: tobiasraabe

pyproject.toml

@@ -24,7 +24,7 @@ dependencies = [
     "click>=8.1.8,!=8.2.0",
     "click-default-group>=1.2.4",
     "msgspec>=0.18.6",
-    "optree>=0.9.0",
+    "optree>=0.16.0",
     "packaging>=23.0.0",
     "pluggy>=1.3.0",
     "rich>=13.8.0",