Update ansible to Open Enclave 0.18.4 (#4501)

getting_started/setup_vm/roles/openenclave/vars/common.yml

@@ -1,6 +1,6 @@
-oe_ver: "0.18.2"
+oe_ver: "0.18.4"
 # Usually the same, except for rc, where ver is -rc and ver_ is _rc
-oe_ver_: "0.18.2"
+oe_ver_: "0.18.4"
 
 # Source install
 workspace: "/tmp/"