PHOENIX-6177 Queryserver Avatica and Jetty versions are incompatible

sync jetty version to avatica 1.17.0
diff --git a/pom.xml b/pom.xml
index dce82dc..98727cd 100644
--- a/pom.xml
+++ b/pom.xml
@@ -80,7 +80,7 @@
         <curator.version>2.12.0</curator.version>
 
         <gson.version>2.2.4</gson.version>
-        <jetty.version>9.4.31.v20200723</jetty.version>
+        <jetty.version>9.4.15.v20190215</jetty.version>
         <commons-io.version>2.5</commons-io.version>
         <commons-collections.version>3.2.2</commons-collections.version>
         <sqlline.version>1.9.0</sqlline.version>