[monitor-aurora-with-grafana] - Update Python version

[houserx-jmcc]

It looks like this example (which works great, thank you!) was built on Python 3.7, and with AWS now discontinuing support for 3.8 (hard cutoff March 2025), it seems 3.9 is the only valid version for this to work on:

observability-best-practices/sandbox/monitor-aurora-with-grafana/README.md

Lines 9 to 10 in 5c7b665

	# Requirements
	- [Python 3.7](https://www.python.org/downloads/). Sample also works with Python 3.8 and 3.9.

If it could be tested/updated to work on more recent versions (a la 3.12) it would help make the code usable going forward. Thanks!