[Versioning] Update changelog for 3.5.1.

In particular:
  1. Removed support for us-iso-east-1.
  2. Added EFa update.

Signed-off-by: Giacomo Marciani <[email protected]>

Author: gmarciani

CHANGELOG.md

@@ -7,7 +7,7 @@ This file is used to list changes made in each version of the AWS ParallelCluste
 ------
 
 **ENHANCEMENTS**
-- Add support for US isolated regions: us-iso-east-1 and us-isob-east-1.
+- Add support for US isolated region us-isob-east-1.
 
 **CHANGES**
 - Upgrade EFA installer to `1.22.0`