Bump jetty-webapp in /sparqlify-web-admin-server

Bumps [jetty-webapp](https://github.com/eclipse/jetty.project) from 9.4.8.v20171121 to 9.4.34.v20201102.
- [Release notes](https://github.com/eclipse/jetty.project/releases)
- [Commits](jetty/jetty.project@jetty-9.4.8.v20171121...jetty-9.4.34.v20201102)

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

sparqlify-web-admin-server/pom.xml

@@ -259,7 +259,7 @@
 <dependency>
     <groupId>org.eclipse.jetty</groupId>
     <artifactId>jetty-webapp</artifactId>
-    <version>9.4.8.v20171121</version>
+    <version>9.4.34.v20201102</version>
     <scope>provided</scope>
 </dependency>