Wording fix

gas.md

@@ -466,7 +466,7 @@ the only available function is an empty 'deposit'.
 
 If the contract code contains a function index when stored, then one does not
 need to load the entire code in order to fail with a function check. However,
-we should not optimize for the exception case, so the question becomes what is
+we should not optimize for the error case, so the question becomes what is
 more efficient for the non-error case. That is not trivial to answer, but for
 now we can "hide" this cost in the codeLoadingCost/codeByteLoadingCost values,
 and we'll make the error case less efficient.