Add East US 2 region to ExpressRoute gateway list

Added East US 2 to the list of available regions for ExpressRoute.

Author: MekaylaMoore

articles/expressroute/scalable-gateway.md

@@ -87,7 +87,7 @@ ErGwScale is available in most Azure regions except:
 * West India
 * West US 2
 * South Central US
-
+* East US 2
 
 ## Pricing