Update jetty jspc maven plugin to 10.0.21

Author: akurtakov

ua/org.eclipse.help.webapp/pom.xml

@@ -25,7 +25,7 @@
       <plugin>
         <groupId>org.eclipse.jetty</groupId>
         <artifactId>jetty-jspc-maven-plugin</artifactId>
-        <version>10.0.20</version>
+        <version>10.0.21</version>
         <executions>
           <execution>
             <id>jspc</id>