Typo in comment only. Spotted by heatsink on #haskell.
-- by @s@, and returns a value of type @a@.
-- The @s@ parameter is either
--
--- * an unstantiated type variable (inside invocations of 'runST'), or
+-- * an uninstantiated type variable (inside invocations of 'runST'), or
--
-- * 'RealWorld' (inside invocations of 'Control.Monad.ST.stToIO').
--