Remove protobuf from top-level pom.xml

This dependency is unused, and does not need to be
version-managed in the top-level pom.xml anymore.

Change-Id: I240d21b6478e15b05e679b8d976af171d81a524e

pom.xml

@@ -175,7 +175,6 @@
     <args4j-version>2.0.12</args4j-version>
     <servlet-api-version>2.5</servlet-api-version>
     <jetty-version>7.6.0.v20120127</jetty-version>
-    <protobuf-version>2.4.0a</protobuf-version>
     <clirr-version>2.4</clirr-version>
   </properties>
 
@@ -421,12 +420,6 @@
         <artifactId>jetty-servlet</artifactId>
         <version>${jetty-version}</version>
       </dependency>
-
-      <dependency>
-        <groupId>com.google.protobuf</groupId>
-        <artifactId>protobuf-java</artifactId>
-        <version>${protobuf-version}</version>
-      </dependency>
     </dependencies>
   </dependencyManagement>