docs(api): update module-methods (#1527)

Remove description about `id` 0 as this `module.id` doesn't 
necessarily mean it is an entry point as it can be affected by
various plugins and the `--optimize-module-order` flag.

Author: akihikodaki

content/api/module-methods.md

@@ -126,13 +126,6 @@ require.resolve(dependency: String)
 
 Synchronously retrieve a module's ID. The compiler will ensure that the dependency is available in the output bundle. See [`module.id`](/api/module-variables#module-id-commonjs-) for more information.
 
-``` javascript
-var id = require.resolve("dependency");
-typeof id === "number";
-id === 0 // if dependency is the entry point
-id > 0 // elsewise
-```
-
 W> Module ID is a number in webpack (in contrast to NodeJS where it is a string -- the filename).