Fix typo in the comment

@@ -66,7 +66,7 @@
  *
  * However, when the "young" bit is cleared, we deny access to the page
  * by clearing the hardware PTE.  Currently Linux does not flush the TLB
- * for us in this case, which means the TLB will retain the transation
+ * for us in this case, which means the TLB will retain the transaction
  * until either the TLB entry is evicted under pressure, or a context
  * switch which changes the user space mapping occurs.