Inline the jetty version property that's used for JSP compilation.

plugins/pom.xml

@@ -53,7 +53,6 @@
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
         <!-- Versions -->
         <openfire.version>4.2.0-SNAPSHOT</openfire.version>
-        <jetty.version>9.2.14.v20151106</jetty.version>
     </properties>
 
     <build>
@@ -116,7 +115,7 @@
                 <plugin>
                     <groupId>org.eclipse.jetty</groupId>
                     <artifactId>jetty-jspc-maven-plugin</artifactId>
-                    <version>${jetty.version}</version>
+                    <version>9.2.14.v20151106</version>
                     <configuration>
                         <webAppSourceDirectory>${project.build.sourceDirectory}/../web</webAppSourceDirectory>
                         <webXml>${project.build.sourceDirectory}/../web/WEB-INF/web.xml</webXml>