Bug 550094 - Update platform to Jetty 9.4.20

Build jsps with 9.4.20 jspc.

Change-Id: Ib35f1d27863d5984c7ec7eacd1d3a8b1fe432a2a
Signed-off-by: Alexander Kurtakov <akurtako@redhat.com>

org.eclipse.help.webapp/pom.xml

diff --git a/org.eclipse.help.webapp/pom.xml b/org.eclipse.help.webapp/pom.xml
index fa76a62..a86f7f6 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>9.4.18.v20190429</version>
+        <version>9.4.20.v20190813</version>
         <executions>
           <execution>
             <id>jspc</id>