Bump jetty version (prometheus#663)

* Bump jetty-server in /simpleclient_jetty

Bumps [jetty-server](https://github.com/eclipse/jetty.project) from 9.0.2.v20130417 to 9.3.27.v20190418.
- [Release notes](https://github.com/eclipse/jetty.project/releases)
- [Commits](jetty/jetty.project@jetty-9.0.2.v20130417...jetty-9.3.27.v20190418)

Signed-off-by: dependabot[bot] <support@github.com>

* Bump jetty-servlet in /simpleclient_jetty

Signed-off-by: Fabian Stäber <fabian@fstab.de>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Fabian Stäber <fabian@fstab.de>

Author: dependabot[bot]

simpleclient_jetty/pom.xml

@@ -40,12 +40,12 @@
         <dependency>
             <groupId>org.eclipse.jetty</groupId>
             <artifactId>jetty-server</artifactId>
-            <version>9.0.2.v20130417</version>
+            <version>9.3.27.v20190418</version>
         </dependency>
         <dependency>
             <groupId>org.eclipse.jetty</groupId>
             <artifactId>jetty-servlet</artifactId>
-            <version>9.0.2.v20130417</version>
+            <version>9.3.27.v20190418</version>
         </dependency>
         <!-- Test Dependencies Follow -->
         <dependency>