ci: avoid titan-06 for Jenkins agents

Jenkinsfile

@@ -12,6 +12,26 @@ spec:
   nodeSelector:
     kubernetes.io/arch: arm64
     node-role.kubernetes.io/worker: "true"
+  affinity:
+    nodeAffinity:
+      requiredDuringSchedulingIgnoredDuringExecution:
+        nodeSelectorTerms:
+          - matchExpressions:
+              - key: kubernetes.io/hostname
+                operator: NotIn
+                values:
+                  - titan-06
+      preferredDuringSchedulingIgnoredDuringExecution:
+        - weight: 100
+          preference:
+            matchExpressions:
+              - key: kubernetes.io/hostname
+                operator: NotIn
+                values:
+                  - titan-13
+                  - titan-15
+                  - titan-17
+                  - titan-19
   containers:
     - name: dind
       image: registry.bstein.dev/bstein/docker:27-dind