Fix: Missing payable at function forceOwnerChange

forceOwnerChange expects ether, and does not have the payable keyword.

docs/common-patterns.rst

@@ -194,6 +194,7 @@ restrictions highly readable.
 
         function forceOwnerChange(address _newOwner)
             public
+            payable
             costs(200 ether)
         {
             owner = _newOwner;