syz-cluster: adjust the limits on parallel processing

Process more patch series in parallel in the prod deployment (we do get
a queue during peak hours) and fewer series in the staging deployment.

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: 7
+    parallelWorkflows: 8
     loreArchives:
       - netdev
       - bpf

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

@@ -8,7 +8,7 @@ metadata:
 data:
   config.yaml: |
     URL: http://unknown
-    parallelWorkflows: 3
+    parallelWorkflows: 2
     loreArchives:
       - netdev
       - linux-ext4