docs(README) Python minimum 3.9 -> 3.10

See also:
- https://devguide.python.org/versions/#:~:text=Release%20manager-,3.9,-PEP%20596
- https://peps.python.org/pep-0596/

Author: tony

README.md

@@ -161,7 +161,7 @@ issue on the tracker.
 
 # More information
 
-- Python support: >= 3.9, pypy
+- Python support: >= 3.10, pypy
 - Source: <https://github.com/git-pull/gp-libs>
 - Docs: <https://gp-libs.git-pull.com>
 - Changelog: <https://gp-libs.git-pull.com/history.html>