Added Ubuntu 20.04 to AiaB requirements

Change-Id: I48fa637c112051cdb7d7cd460215b111ab7a5686
diff --git a/developer/aiabhw.rst b/developer/aiabhw.rst
index 6cdf3dc..6003240 100644
--- a/developer/aiabhw.rst
+++ b/developer/aiabhw.rst
@@ -49,7 +49,7 @@
 Perform these steps to prepare the server for the AiaB install:
 
 * Connect the server to the local network
-* Perform a clean install of Ubuntu 18.04 on the server
+* Perform a clean install of Ubuntu 18.04 or Ubuntu 20.04 on the server
 * Set up password-less sudo for the user that will install Aether-in-a-Box
 
 After the steps above have been completed, install Aether-in-a-Box as follows::