Cleanup basic buttons

Author: FrederikSchlemmer

src/material-examples/button-types/button-types-example.html

@@ -6,8 +6,6 @@ <h3>Basic Buttons</h3>
   <button mat-button color="warn">Warn</button>
   <button mat-button disabled>Disabled</button>
   <a mat-button routerLink=".">Link</a>
-  <button mat-stroked-button>Strocked</button>
-  <button mat-flat-button>Flat</button>
 </div>
 
 <h3>Raised Buttons</h3>