delete unnecessary blank lines

Signed-off-by: Bevisy Zhang <binbin36520@gmail.com>

image/spec/v1.1.md

@@ -405,9 +405,7 @@ whitespace. It has been added to this example for clarity.
             filesystem).
           </li>
         </ul>
-
 Here is an example history section:
-
 <pre>"history": [
   {
     "created": "2015-10-31T22:22:54.690851953Z",