Remove unnecessary closed? guard

The debugger can't jump back to this point, so we don't have to worry
about this code executing twice.

Library/Homebrew/formula.rb

@@ -529,7 +529,7 @@ class Formula
             puts buf
           end
         ensure
-          rd.close unless rd.closed?
+          rd.close
         end
       else
         pid = fork { exec_cmd(cmd, args, log, logfn) }