Install python 3.9 for al2

Author: hgreebe

cookbooks/aws-parallelcluster-shared/attributes/versions.rb

@@ -1,6 +1,6 @@
 # Python Version
 default['cluster']['python-version'] = '3.12.8'
-if alinux2?
+if platform?('amazon') && node['platform_version'] == "2"
   default['cluster']['python-version'] = '3.9.20'
 end
 default['cluster']['python-major-minor-version'] = '3.12'