Remove old traces of typings.

In the commit akveo/ng2-admin@e7fca6d4, we moved to @types for TypeScript typings.

It remains some traces in the documentation. This commit remove them.

src/vendor.browser.ts

@@ -1,7 +1,7 @@
 // For vendors for example jQuery, Lodash, angular2-jwt just import them here unless you plan on
 // chunking vendors files for async loading. You would need to import the async loaded vendors
 // at the entry point of the async loaded file. Also see custom-typings.d.ts as you also need to
-// run `typings install x` where `x` is your module
+// run `npm install @types/x` where `x` is your module
 
 // Angular 2
 import '@angular/platform-browser';