Bug 551763 - Update platform to Jetty 9.4.21

Build jsps with respective jspc maven plugin.

Change-Id: I3fb75a0e9d98baa691f23da62dea37f4a89768f7
Signed-off-by: Alexander Kurtakov <akurtako@redhat.com>
diff --git a/org.eclipse.help.webapp/pom.xml b/org.eclipse.help.webapp/pom.xml
index a150e50..c2a1677 100644
--- a/org.eclipse.help.webapp/pom.xml
+++ b/org.eclipse.help.webapp/pom.xml
@@ -25,7 +25,7 @@
       <plugin>
         <groupId>org.eclipse.jetty</groupId>
         <artifactId>jetty-jspc-maven-plugin</artifactId>
-        <version>9.4.20.v20190813</version>
+        <version>9.4.21.v20190926</version>
         <executions>
           <execution>
             <id>jspc</id>