Revise lab instructions for ExpressRoute gateway setup

Updated the lab instructions for configuring an ExpressRoute gateway, including details on tasks, settings, and learning resources.

Author: staleycyn

Instructions/Exercises/M03-Unit 4 Configure an ExpressRoute Gateway.md

@@ -1,7 +1,7 @@
 ---
 lab:
   title: M03-Unit 4 Configure an ExpressRoute Gateway
-  description: Configure an ExpressRoute Gateway
+  description: Configure an ExpressRoute gateway.
   duration: 60 minutes
   level: 300
   islab: true
@@ -126,3 +126,4 @@ Congratulations on completing the lab. Here are the main takeaways for this lab.
 
 
 
+