config: temporarily disable kola-openstack in the pipeline

All openstack runs started failing today due to
coreos#1061
Stop running tests on openstack for the next few days to see
if the issue is resolved after the weekend.

Author: marmijo

config.yaml

@@ -110,7 +110,7 @@ clouds:
       - "fedora-coreos-${STREAM}"
       - "https://compute.googleapis.com/compute/v1/projects/vm-options/global/licenses/enable-vmx"
   openstack:
-    test_architectures: [x86_64, aarch64]
+    test_architectures: []
 
 misc:
   versionary: true