fix some mixed space+tab indentation

This fixes all instances of " \t" in the code base. Most common case
seems to be after a "where" line; probably vim copied the two space layout
of that line.

Done as a background task while listening to episode 2 of the Type Theory
podcast.

Git/Version.hs

@@ -21,7 +21,7 @@ instance Show GitVersion where
 installed :: IO GitVersion
 installed = normalize . extract <$> readProcess "git" ["--version"]
   where
-  	extract s = case lines s of
+	extract s = case lines s of
 		[] -> ""
 		(l:_) -> unwords $ drop 2 $ words l