[#162] Remove artificial delay in allowRewrite

Problem: `allowRewrite` uses `threadDelay (ms 100)` to "prevent our
output to interleave with further outputs".

It's not exactly what problem this is supposed to address, and how it's
supposed to fix it. This seems like it may have been an earlier attempt
to fix the issue addressed in the previous commit.

Solution: delete `threadDelay`.

src/Xrefcheck/Progress.hs

@@ -31,7 +31,7 @@ import Universum
 
 import Data.Ratio ((%))
 import System.Console.Pretty (Color (..), Style (..), color, style)
-import Time (Second, Time, ms, sec, threadDelay, unTime, (-:-))
+import Time (Second, Time, sec, unTime, (-:-))
 
 -----------------------------------------------------------
 -- Task timestamp
@@ -225,8 +225,6 @@ allowRewrite enabled = bracket prepare erase
     erase (Rewrite RewriteCtx{..}) = liftIO $ do
       maxPrintedSize <- readIORef rMaxPrintedSize
       hPutStr stderr $ '\r' : replicate maxPrintedSize ' ' ++ "\r"
-      -- prevent our output to interleave with further outputs
-      threadDelay (ms 100)
     erase RewriteDisabled = pass
 
 -- | Return caret and print the given text.