message: docs(scheduler): remove link to Stackblitz example
  Remove link to Stackblitz example because each code snippet provides such link anyway.
diff: In the example below, we take the usual simple Observable that emits values `1`, `2`, `3` synchronously, and use the operator `observeOn` to specify the `async` scheduler to use for delivering those values.
  -[View on Stackblitz](https://stackblitz.com/edit/typescript-jexdny)
  ```ts
  import { Observable, asyncScheduler } from 'rxjs';
  import { observeOn } from 'rxjs/operators';
  