dev-plugins.txt: Recommend ServletModule instead of HttpPluginModule

As first noted in Ice22b3c23, HttpPluginModule is not appropriate to
extend because its configure method contains a bunch of bindings that
are specific to core; we're just lucky that it was harmless in practice.

Change-Id: I3b89150d18f41b164f350ff3f9649b9bc66880db
diff --git a/Documentation/dev-plugins.txt b/Documentation/dev-plugins.txt
index f2bd273e..721d8db 100644
--- a/Documentation/dev-plugins.txt
+++ b/Documentation/dev-plugins.txt
@@ -889,7 +889,7 @@
   public boolean all = false;
 }
 
-public static class HttpModule extends HttpPluginModule {
+public static class HttpModule extends ServletModule {
   @Override
   protected void configureServlets() {
     bind(DynamicBean.class)
@@ -1661,7 +1661,7 @@
 
 [source,java]
 ----
-public class HttpModule extends HttpPluginModule {
+public class HttpModule extends ServletModule {
   @Override
   protected void configureServlets() {
     DynamicSet.bind(binder(), WebUiPlugin.class)
@@ -2205,9 +2205,9 @@
 /** Register the LfsApiServlet to listen on the default LFS protocol endpoint */
 import static com.google.gerrit.httpd.plugins.LfsPluginServlet.URL_REGEX;
 
-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() {