chore(docs): remove usage of ng2-bootstrap/ng2-bootstrap Deprecated (valor-software#1443)

New version of angular-cli displays deprecated warning:
ng2-bootstrap.js: 5 
DEPRECATED: please replace import of `ng2-bootstrap/ng2-bootstrap` with `ng2-bootstrap`

Author: antcalatayud

docs/getting-started/ng-cli.md

@@ -24,7 +24,7 @@ ng serve
 - open `src/app/app.module.ts` and add
 
 ```typescript
-import { AlertModule } from 'ng2-bootstrap/ng2-bootstrap';
+import { AlertModule } from 'ng2-bootstrap';
 ...
 
 @NgModule({