Remove return values of pause() and unpause() of Pausable

contracts/lifecycle/Pausable.sol

@@ -34,18 +34,16 @@ contract Pausable is Ownable {
   /**
    * @dev called by the owner to pause, triggers stopped state
    */
-  function pause() onlyOwner whenNotPaused returns (bool) {
+  function pause() onlyOwner whenNotPaused {
     paused = true;
     Pause();
-    return true;
   }
 
   /**
    * @dev called by the owner to unpause, returns to normal state
    */
-  function unpause() onlyOwner whenPaused returns (bool) {
+  function unpause() onlyOwner whenPaused {
     paused = false;
     Unpause();
-    return true;
   }
 }