Update end-of-life date

[edthedev]

Context

README.md has an end of life date of last October, based on this code initially being developed for Python 3.9 on Splunk SOAR. The SOAR python version is updated, and this code has been tested under newer Python versions than 3.9, and works fine.

Let's update our README to reflect.

[edthedev]

Per https://github.com/techservicesillinois/soar-clearpass/blob/main/tests/test_python_version.py - we are using this under Python 3.13.