Bump jetty-webapp in /Stepik.org/L1.1 Simple web server

Bumps [jetty-webapp](https://github.com/eclipse/jetty.project) from 9.3.0.M0 to 9.4.34.v20201102.
- [Release notes](https://github.com/eclipse/jetty.project/releases)
- [Commits](jetty/jetty.project@jetty-9.3.0.M0...jetty-9.4.34.v20201102)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

Stepik.org/L1.1 Simple web server/pom.xml

@@ -55,7 +55,7 @@
         <dependency>
             <groupId>org.eclipse.jetty</groupId>
             <artifactId>jetty-webapp</artifactId>
-            <version>9.3.0.M0</version>
+            <version>9.4.34.v20201102</version>
         </dependency>
 
     </dependencies>