docs: add comment explaining PYTHON_VERSION / abi3 relationship

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: cpsievert

.github/workflows/python-release.yml

@@ -10,6 +10,9 @@ permissions:
   contents: read
 
 env:
+  # Must match the abi3-py3XX feature in ggsql-python/Cargo.toml.
+  # abi3 wheels built against 3.10 are forward-compatible with all later
+  # Python versions, so this should be the minimum supported version.
   PYTHON_VERSION: "3.10"
   NODE_VERSION: "20"