syz-cluster: run more workflows in parallel

At times, the series still have to queue until we have started
processing them.

Author: a-nogikh

syz-cluster/overlays/gke/prod/global-config.yaml

@@ -8,7 +8,7 @@ metadata:
 data:
   config.yaml: |
     URL: https://ci.syzbot.org
-    parallelWorkflows: 8
+    parallelWorkflows: 10
     loreArchives:
       - netdev
       - bpf