Bump jettyVersion from 9.4.27.v20200227 to 9.4.29.v20200521

Bumps `jettyVersion` from 9.4.27.v20200227 to 9.4.29.v20200521.

Updates `jetty-server` from 9.4.27.v20200227 to 9.4.29.v20200521
- [Release notes](https://github.com/eclipse/jetty.project/releases)
- [Commits](jetty/jetty.project@jetty-9.4.27.v20200227...jetty-9.4.29.v20200521)

Updates `jetty-servlet` from 9.4.27.v20200227 to 9.4.29.v20200521
- [Release notes](https://github.com/eclipse/jetty.project/releases)
- [Commits](jetty/jetty.project@jetty-9.4.27.v20200227...jetty-9.4.29.v20200521)

Updates `jetty-servlets` from 9.4.27.v20200227 to 9.4.29.v20200521
- [Release notes](https://github.com/eclipse/jetty.project/releases)
- [Commits](jetty/jetty.project@jetty-9.4.27.v20200227...jetty-9.4.29.v20200521)

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

Author: dependabot-preview[bot]

build.gradle

@@ -37,7 +37,7 @@ subprojects {
         guiceVersion = '4.2.3'
         jacksonVersion = '2.10.3'
         javassistVersion = '3.27.0-GA'
-        jettyVersion = '9.4.27.v20200227'
+        jettyVersion = '9.4.29.v20200521'
         log4jVersion = '2.13.1'
         nettyVersion = '4.1.50.Final'
         slf4jVersion = '1.7.30'