pin ZooKeeper dependencies to 3.5.x (#11354)

diff --git a/.github/dependabot.yml b/.github/dependabot.yml
index 70b92b3..717d6a0 100644
--- a/.github/dependabot.yml
+++ b/.github/dependabot.yml
@@ -6,3 +6,6 @@
       interval: "daily"
     ignore:
       - dependency-name: "com.google.guava:guava"
+      # pin ZooKeeper dependencies to 3.5.x
+      - dependency-name: "org.apache.zookeeper"
+        versions: "[3.6,)"