Remove Alibaba reference

Author: Shubha Narayanan

modules/supported-platforms-for-openshift-clusters.adoc

@@ -9,7 +9,6 @@
 
 In {product-title} {product-version}, you can install a cluster that uses installer-provisioned infrastructure on the following platforms:
 
-* Alibaba Cloud
 * Amazon Web Services (AWS)
 * Bare metal
 * Google Cloud Platform (GCP)