Remove Python requirement from the README

This is already specified in the pyproject.toml file, and pip should
take care of checking it, so having it in the README is redundant. It
also requires maintainance, as each time we support another Python
version it needs to be updated.

Signed-off-by: Leandro Lucarella <[email protected]>

Author: llucax

README.md

@@ -6,10 +6,6 @@
 
 A development kit to interact with the Frequenz development platform.
 
-## Supported Python versions
-
-* Only Python 3.11 is fully supported (tested).
-
 ## Contributing
 
 If you want to know how to build this project and contribute to it, please