Add me-central1 GCP region as supported region

Author: makentenza

modules/installation-gcp-regions.adoc

@@ -32,6 +32,7 @@ regions:
 * `europe-west8` (Milan, Italy)
 * `europe-west9` (Paris, France)
 * `europe-west12` (Turin, Italy)
+* `me-central1` (Doha, Qatar, Middle East)
 * `me-west1` (Tel Aviv, Israel)
 * `northamerica-northeast1` (Montréal, Québec, Canada)
 * `northamerica-northeast2` (Toronto, Ontario, Canada)