Use minimal clusters for E2E

We don't really need to run the entire E2E suite anymore since we're
deploying the operator and it takes care of the entire deployment cycle.
Hence, the testing on operator should suffice and the helm testing can
be much slimmer and only use 2 single-node clusters.

This won't run the non-gw node tests, but as it's all tested on the
operator anyhow, there's no need to re-test it here.

Signed-off-by: Mike Kolesnik <mkolesni@redhat.com>

.shipyard.e2e.ovn.yml

@@ -1,7 +1,7 @@
 ---
 cni: ovn
 submariner: true
-nodes: control-plane worker worker
+nodes: control-plane
 clusters:
   cluster1:
   cluster2:

.shipyard.e2e.yml

@@ -1,7 +1,7 @@
 ---
 cni: weave
 submariner: true
-nodes: control-plane worker
+nodes: control-plane
 clusters:
   cluster1:
   cluster2: