Delete ant build/util targets for demo site updates as they are now absolete (#2789)

- Followup to PR #2773, where we started using official appengine Maven plugin than older ```maven-gae-plugin```
- ```appcfg``` script is deprecated and most of these works can be done through ```gcloud-appengine-sdk```
- More details in cl/333435946 (where we moved away from ```appcfg``` during the releases) and cl/xxxxx (We no more need any manual copy jar commands)

java/demo/build.xml

@@ -1,59 +0,0 @@
-<project>
-  <property name="appengine-sdk.dir" location="../../appengine-java-sdk" />
-
-  <import file="${appengine-sdk.dir}/config/user/ant-macros.xml" />
-
-  <path id="project.classpath">
-    <pathelement path="war/WEB-INF/classes" />
-    <fileset dir="war/WEB-INF/lib">
-      <include name="**/*.jar" />
-    </fileset>
-    <fileset dir="${appengine-sdk.dir}/lib">
-      <include name="shared/**/*.jar" />
-    </fileset>
-  </path>
-
-  <target name="copyjars" description="Copies the App Engine JARs to the WAR.">
-    <copy todir="war/WEB-INF/lib" flatten="true">
-      <fileset dir="${appengine-sdk.dir}/lib/user">
-        <include name="**/*.jar" />
-      </fileset>
-    </copy>
-  </target>
-
-  <target name="compile" depends="copyjars"
-          description="Compiles Java source and copies other source files to the WAR.">
-    <mkdir dir="war/WEB-INF/classes" />
-    <copy todir="war/WEB-INF/classes">
-      <fileset dir="src">
-        <exclude name="**/*.java" />
-      </fileset>
-    </copy>
-    <javac srcdir="src" destdir="war/WEB-INF/classes" classpathref="project.classpath" debug="on"
-           includeAntRuntime="false" source="1.8" target="1.8"/>
-  </target>
-
-  <target name="runserver" depends="compile" description="Starts the development server.">
-    <dev_appserver war="war" />
-  </target>
-
-  <target name="update" depends="compile" description="Uploads the application to App Engine.">
-    <appcfg action="update" war="war" />
-  </target>
-
-  <target name="rollback" depends="compile"
-          description="Rolls back an interrupted application update.">
-    <appcfg action="rollback" war="war" />
-  </target>
-
-  <target name="request_logs" description="Downloads log data from App Engine for the application.">
-    <appcfg action="request_logs" war="war">
-      <options>
-        <arg value="--num_days=5"/>
-      </options>
-      <args>
-        <arg value="logs.txt"/>
-      </args>
-    </appcfg>
-  </target>
-</project>