Replace removeDirectoryRecursive with removePathForcibly

[Bodigrim]

There are several instances of code like this:

deletePackageDB :: FilePath -> IO ()
deletePackageDB dbPath = do
  -- currently one impl for all compiler flavours, but could change if needed
  dir_exists <- doesDirectoryExist dbPath
  if dir_exists
    then removeDirectoryRecursive dbPath
    else do
      file_exists <- doesFileExist dbPath
      when file_exists $ removeFile dbPath

This is very excessive, a single removePathForcibly would do the trick.