Update pom.xml

Update pom in order to have Accumulo-Examples zookeeper version match  version of current accumulo-snapshot. Reverted from ZK 3.6.2 to 3.5.9.

pom.xml

@@ -35,7 +35,7 @@
     <maven.compiler.release>11</maven.compiler.release>
     <maven.compiler.source>11</maven.compiler.source>
     <maven.compiler.target>11</maven.compiler.target>
-    <zookeeper.version>3.6.2</zookeeper.version>
+    <zookeeper.version>3.5.9</zookeeper.version>
   </properties>
   <dependencyManagement>
     <dependencies>