docs: update minimum Python version to 3.10

The install section still stated Python 3.9 as the minimum. Python 3.9
support was dropped on this branch (pyproject.toml now requires >=3.10),
so align the README with the actual requirement.

Author: pcaro

README.md

@@ -17,7 +17,7 @@ play with the CloudBlue Connect API using a python REPL like [jupyter](https://j
 
 ## Install
 
-`Connect Python OpenAPI Client` requires python 3.9 or later.
+`Connect Python OpenAPI Client` requires python 3.10 or later.
 
 
 `Connect Python OpenAPI Client` can be installed from [pypi.org](https://pypi.org/project/connect-openapi-client/) using pip: