Cleanup packager dead debug endpoint

Summary:
When trying to access the debug dependency graph through the `/debug/graph` endpoint of the packager server (documented in the packager README and listed as well when hitting the root `/debug` endpoint), all I am getting back is a nasty HTTP 500 error :'(

What triggers this HTTP 500 is a `TypeError` being thrown while trying to access a function that doesn't exists (anymore). Here is the error log of the packager when trying to access this endpoint :

```
TypeError: this._depGraph.getDebugInfo is not a function
    at Resolver.getDebugInfo (index.js:270:27)
    at Bundler.getGraphDebugInfo (index.js:575:27)
    at Server._processDebugRequest (index.js:369:28)
    at Server.processRequest (index.js:423:12)
    at next (/Users/blemair/Code/DependencyGraphTest/node_modules/connect/lib/proto.js:174:15)
    at Object.module.exports [as handle] (cpuProfilerMiddleware.js:17:5)
    at next (/Users/blemair/Code/DependencyGraphTest/node_modules/connect/lib/proto.js:174:15)
    at Object.module.exports [as
Closes https://github.com/facebook/react-native/pull/8117

Differential Revision: D3445582

fbshipit-source-id: cf5af8bbba293f39773f32814a3b388b7ff67bf7

README.md

@@ -72,12 +72,10 @@ Here are the current options the packager accepts:
 
 ### /debug
 
-This is a page used for debugging, it has links to two pages:
+This is a page used for debugging, it offers a link to a single page :
 
 * Cached Packages: which shows you the packages that's been already
   generated and cached
-* Dependency Graph: is the in-memory graph of all the modules and
-  their dependencies
 
 ## Programmatic API
 

react-packager/src/Bundler/index.js

@@ -566,10 +566,6 @@ class Bundler {
     });
   }
 
-  getGraphDebugInfo() {
-    return this._resolver.getDebugInfo();
-  }
-
   _generateAssetModule_DEPRECATED(bundle, module, getModuleId) {
     return Promise.all([
       sizeOf(module.path),

react-packager/src/Resolver/index.js

@@ -265,10 +265,6 @@ class Resolver {
   minifyModule({path, code, map}) {
     return this._minifyCode(path, code, map);
   }
-
-  getDebugInfo() {
-    return this._depGraph.getDebugInfo();
-  }
 }
 
 function defineModuleCode(moduleName, code, verboseName = '', dev = true) {

react-packager/src/Server/index.js

@@ -348,7 +348,6 @@ class Server {
     const parts = pathname.split('/').filter(Boolean);
     if (parts.length === 1) {
       ret += '<div><a href="/debug/bundles">Cached Bundles</a></div>';
-      ret += '<div><a href="/debug/graph">Dependency Graph</a></div>';
       res.end(ret);
     } else if (parts[1] === 'bundles') {
       ret += '<h1> Cached Bundles </h1>';
@@ -365,10 +364,6 @@ class Server {
           console.log(e.stack); // eslint-disable-line no-console-disallow
         }
       );
-    } else if (parts[1] === 'graph'){
-      ret += '<h1> Dependency Graph </h2>';
-      ret += this._bundler.getGraphDebugInfo();
-      res.end(ret);
     } else {
       res.writeHead('404');
       res.end('Invalid debug request');