t: drop debug cat calls

We `cat` files, but don't inspect or grab the contents in any way.
Unlike in an earlier commit, there is no reason to suspect that these
files could be missing, so `cat`-ing them is just wasted effort.

Signed-off-by: Martin Ågren <martin.agren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t2107-update-index-basic.sh

@@ -9,7 +9,6 @@ Tests for command-line parsing and basic operation.
 
 test_expect_success 'update-index --nonsense fails' '
 	test_must_fail git update-index --nonsense 2>msg &&
-	cat msg &&
 	test -s msg
 '