Remove trailing whitespace

Summary:

Test Plan:

src/Development/Shake/Util.hs

@@ -17,7 +17,7 @@ import Data.IORef
 import Data.Maybe
 import Control.Monad.Extra
 import System.IO.Extra as IO
- 
+
 
 -- | Given the text of a Makefile, extract the list of targets and dependencies. Assumes a
 --   small subset of Makefile syntax, mostly that generated by @gcc -MM@.