OCPBUGS-13670: Added poland central zone to Azure docs

Author: dfitzmau

modules/installation-azure-regions.adoc

@@ -37,6 +37,7 @@ The installation program dynamically generates the list of available Microsoft A
 * `northcentralus` (North Central US)
 * `northeurope` (North Europe)
 * `norwayeast` (Norway East)
+* `polandcentral` (Poland Central)
 * `qatarcentral` (Qatar Central)
 * `southafricanorth` (South Africa North)
 //* southafricawest (South Africa West)