docs: fix typos

Closes #4308

modules/angular2/src/core/pipes/date_pipe.ts

@@ -49,7 +49,7 @@ var defaultLocale: string = 'en-US';
  *  | timezone  |   Z    | Z (GMT-8:00) | -                 | -         | -         |
  *
  * In javascript, only the components specified will be respected (not the ordering,
- * punctuations, ...) and details of the the formatting will be dependent on the locale.
+ * punctuations, ...) and details of the formatting will be dependent on the locale.
  * On the other hand in Dart version, you can also include quoted text as well as some extra
  * date/time components such as quarter. For more information see:
  * https://api.dartlang.org/apidocs/channels/stable/dartdoc-viewer/intl/intl.DateFormat.

modules/angular2/src/core/pipes/number_pipe.ts

@@ -59,7 +59,7 @@ export class NumberPipe {
  * WARNING: this pipe uses the Internationalization API.
  * Therefore it is only reliable in Chrome and Opera browsers.
  *
- * Formats a number as local text. i.e. group sizing and seperator and other locale-specific
+ * Formats a number as local text. i.e. group sizing and separator and other locale-specific
  * configurations are based on the active locale.
  *
  * # Usage