t9810: drop debug `cat` call

We `cat` kwdelfile.c, but don't inspect or grab the contents in any way. This looks like a remnant from a debug session. Similar to the previous commit, one could argue that `cat`-ing the file verifies that it didn't disappear somehow. But because the very next thing we do after `cat`-ing the file is to `grep` in it, we can safely drop the call to `cat`. Signed-off-by: Martin Ågren <martin.agren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>