docs: add DI to public docs

modules/angular2/test/di/key_spec.js

@@ -21,31 +21,5 @@ export function main() {
       expect(registry.get(registry.get('car'))).toBe(registry.get('car'));
     });
 
-    describe("metadata", function () {
-      it("should assign metadata to a key", function () {
-        var key = registry.get('car');
-
-        Key.setMetadata(key, "meta");
-
-        expect(key.metadata).toEqual("meta");
-      });
-
-      it("should allow assigning the same metadata twice", function () {
-        var key = registry.get('car');
-
-        Key.setMetadata(key, "meta");
-        Key.setMetadata(key, "meta");
-
-        expect(key.metadata).toEqual("meta");
-      });
-
-      it("should throw when assigning different metadata", function () {
-        var key = registry.get('car');
-
-        Key.setMetadata(key, "meta1");
-
-        expect(() => Key.setMetadata(key, "meta2")).toThrowError();
-      });
-    });
   });
 }