Fixed some bugs in documentation. Add CallOpInterfaceHandle to the
arguments of ChangeCallTargetOp, after doing so the section described in
the documentation works correctly, Otherwise the following code reports
an error.
```
// Cast to our new type.
%casted = transform.cast %call : !transform.any_op to !transform.my.call_op_interface
// Using our new operation.
transform.my.change_call_target %casted, "microkernel" : !transform.my.call_op_interface
```
1a4f0d6115