Remove Ubuntu 20.04 as a supported OS due to OAISIM issues
Change-Id: Ibd9d1bac067491d1b75f37e77cfb16cacde7428f
diff --git a/developer/aiab.rst b/developer/aiab.rst
index a75c2b3..0498a3d 100644
--- a/developer/aiab.rst
+++ b/developer/aiab.rst
@@ -23,7 +23,7 @@
AiaB can be run on a bare metal machine or VM. System prerequisites:
-* Ubuntu 18.04 or Ubuntu 20.04 clean install
+* Ubuntu 18.04 clean install (18.04 is a requirement of OAISIM which is used to test 4G Aether)
* Kernel 4.15 or later
* Haswell CPU or newer
* At least 4 CPUs and 12GB RAM