Fix typo in CABI code

Author: lukewagner

design/mvp/CanonicalABI.md

@@ -506,7 +506,7 @@ arbitrarily interleave.)
   def trap_if_on_the_stack(self, inst):
     c = self.caller
     while c is not None:
-      trap_if(c.inst is int)
+      trap_if(c.inst is inst)
       c = c.caller
 ```
 By analyzing a linked component DAG, an optimized implementation can avoid the

design/mvp/canonical-abi/definitions.py

@@ -417,7 +417,7 @@ async def enter(self):
   def trap_if_on_the_stack(self, inst):
     c = self.caller
     while c is not None:
-      trap_if(c.inst is int)
+      trap_if(c.inst is inst)
       c = c.caller
 
   def create_borrow(self):