Extend ServletModule instead of HttpPluginModule

As described in I3b89150d1.

Change-Id: Ic91ce95719c6bccc73cc29a2139a2274f20d1939

src/main/java/com/googlesource/gerrit/plugins/importer/HttpModule.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/importer/HttpModule.java b/src/main/java/com/googlesource/gerrit/plugins/importer/HttpModule.java
index 79fe837..c4f7c15 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/importer/HttpModule.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/importer/HttpModule.java
@@ -18,9 +18,9 @@
 import com.google.gerrit.extensions.webui.GwtPlugin;
 import com.google.gerrit.extensions.webui.JavaScriptPlugin;
 import com.google.gerrit.extensions.webui.WebUiPlugin;
-import com.google.gerrit.httpd.plugins.HttpPluginModule;
+import com.google.inject.servlet.ServletModule;
 
-public class HttpModule extends HttpPluginModule {
+public class HttpModule extends ServletModule {
   @Override
   protected void configureServlets() {
     DynamicSet.bind(binder(), WebUiPlugin.class)