[FAB-11075] Change default arch to amd64

Change-Id: Id28aa76197d922cf98723ef9f62e34a11bc46aa1
Signed-off-by: Bob Stasyszyn <Bob.Stasyszyn@securekey.com>

Author: bstasyszyn

test/fixtures/dockerenv/.env

@@ -9,7 +9,7 @@
 # variables. See docker compose documentation.
 
 # Default architecture for fabric images
-FABRIC_ARCH=x86_64
+FABRIC_ARCH=amd64
 FABRIC_ARCH_SEP=-
 
 CORE_PEER_NETWORKID=fabsdkgo