Bump jetty-server in /examples/basic-http (#228)

Bumps [jetty-server](https://github.com/eclipse/jetty.project) from 9.4.28.v20200408 to 9.4.30.v20200611.
- [Release notes](https://github.com/eclipse/jetty.project/releases)
- [Commits](https://github.com/eclipse/jetty.project/compare/jetty-9.4.28.v20200408...jetty-9.4.30.v20200611)

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examples/basic-http/pom.xml

@@ -41,7 +41,7 @@
         <dependency>
             <groupId>org.eclipse.jetty</groupId>
             <artifactId>jetty-server</artifactId>
-            <version>9.4.28.v20200408</version>
+            <version>9.4.30.v20200611</version>
         </dependency>
     </dependencies>
 </project>