ghci: remove unused showBreakArray function

GHCi.BreakArray.showBreakArray is not used anywhere, hence the
housecleaning.

(cherry picked from commit 2d6a63ab)

libraries/ghci/GHCi/BreakArray.hs

@@ -30,11 +30,9 @@ module GHCi.BreakArray
     , setupBreakpoint
     , breakOn
     , breakOff
-    , showBreakArray
     ) where
 
 import Prelude -- See note [Why do we import Prelude here?]
-import Control.Monad
 
 import GHC.Exts
 import GHC.IO ( IO(..) )
@@ -48,13 +46,6 @@ breakOff, breakOn :: Int
 breakOn  = 0
 breakOff = -1
 
-showBreakArray :: BreakArray -> IO ()
-showBreakArray array = do
-    forM_ [0 .. (size array - 1)] $ \i -> do
-        val <- readBreakArray array i
-        putStr $ ' ' : show val
-    putStr "\n"
-
 setupBreakpoint :: BreakArray -> Int -> Int -> IO Bool
 setupBreakpoint breakArray ind val
     | safeIndex breakArray ind = do