Fix sdk-benchmarks version (#3459)

Author: zoewangg

test/sdk-benchmarks/pom.xml

@@ -234,7 +234,7 @@
             <dependency>
                 <groupId>org.eclipse.jetty</groupId>
                 <artifactId>jetty-bom</artifactId>
-                <version>9.4.15.v20190215</version>
+                <version>${jetty.version}</version>
                 <type>pom</type>
                 <scope>import</scope>
             </dependency>