docs(contribute): update compatible Python versions in local environm…

…ent setup instructions (apache#20260)

* Remove incompatible Python 3.7 from local env setup docs

* Ensure Python 3.8 or 3.9

Co-authored-by: Diego Martin <diego.martin@indigitall.com>

CONTRIBUTING.md

@@ -420,7 +420,7 @@ Commits to `master` trigger a rebuild and redeploy of the documentation site. Su
 Make sure your machine meets the [OS dependencies](https://superset.apache.org/docs/installation/installing-superset-from-scratch#os-dependencies) before following these steps.
 You also need to install MySQL or [MariaDB](https://mariadb.com/downloads).
 
-Ensure that you are using Python version 3.7 or 3.8, then proceed with:
+Ensure that you are using Python version 3.8 or 3.9, then proceed with:
 
 ```bash
 # Create a virtual environment and activate it (recommended)