Merge pull request nestjs#4022 from mvegter/patch-1

docs(): fixed two typos in the docs

Author: kamilmysliwiec

CONTRIBUTING.md

@@ -236,8 +236,8 @@ Footer should contain a [closing reference to an issue](https://help.github.com/
 Samples: (even more [samples](https://github.com/nestjs/nest/commits/master))
 
 ```
-docs(changelog) update change log to beta.5
-bugfix(core) need to depend on latest rxjs and zone.js
+docs(changelog): update change log to beta.5
+bugfix(core): need to depend on latest rxjs and zone.js
 ```
 
 ### Revert

packages/common/exceptions/service-unavailable.exception.ts

@@ -10,7 +10,7 @@ import { HttpStatus } from '../enums/http-status.enum';
  */
 export class ServiceUnavailableException extends HttpException {
   /**
-   * Instnatiate a `ServiceUnavailableException` Exception.
+   * Instantiate a `ServiceUnavailableException` Exception.
    *
    * @example
    * `throw new ServiceUnavailableException()`