Fixup doctest readNew blockRam

Author: leonschoorl

clash-prelude/src/Clash/Prelude/BlockRam.hs

@@ -850,6 +850,8 @@ readNew (blockRam (0 :> 1 :> Nil))
 >>> :t readNew (blockRam (0 :> 1 :> Nil))
 readNew (blockRam (0 :> 1 :> Nil))
   :: ...
+     ...
+     ...
      ... =>
      Signal dom addr -> Signal dom (Maybe (addr, a)) -> Signal dom a