Support Process changes in 0.24 (fixes #166)

This should be merged once we release 0.24 (and it depends on minitest.cr: ysbaddaden/minitest.cr#22)

src/resolvers/git.cr

@@ -222,7 +222,7 @@ module Shards
       Dir.cd(path) do
         Shards.logger.debug command
 
-        output = capture ? IO::Memory.new : false
+        output = capture ? IO::Memory.new : Process::Redirect::Close
         error = IO::Memory.new
         status = Process.run("/bin/sh", input: IO::Memory.new(command), output: output, error: error)