Fix typo

Co-authored-by: Joel Dice <joel.dice@fermyon.com>

design/mvp/CanonicalABI.md

@@ -604,7 +604,7 @@ callback instead of simply returning the values from `canon_lift` enables the
 callee to keep executing after returning its results. There is a dynamic error
 if `task.return` is not called exactly once and if the callee has not dropped
 all borrowed handles by the time `task.return` is called. This means that the
-caller can assume that ownership all its lent borrowed handles has been
+caller can assume that ownership of all its lent borrowed handles has been
 returned to it when it is notified that the `Subtask` has reached the
 `RETURNED` state.
 ```python