Fix type annotation in CanonicalABI.md

Author: lukewagner

design/mvp/canonical-abi/definitions.py

@@ -344,7 +344,7 @@ class BorrowHandle(Handle):
 
 class BorrowScope:
   borrow_count: int
-  lenders: [OwnHandle]
+  lenders: [Handle]
 
   def __init__(self):
     self.borrow_count = 0