t9001: mark the script as no longer leak checker clean

The test uses "format-patch --thread" which is known to leak the
generated message ID list.

Plugging these leaks involves straightening out the memory ownership
rules around rev_info.message_id and rev_info.ref_message_ids, and
is beyond the scope of send-email fix, so for now mark the test as
leaky to unblock the topic before the release.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t9001-send-email.sh

@@ -4,7 +4,7 @@ test_description='git send-email'
 GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=main
 export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
 
-TEST_PASSES_SANITIZE_LEAK=true
+# no longer TEST_PASSES_SANITIZE_LEAK=true - format-patch --thread leaks
 . ./test-lib.sh
 
 # May be altered later in the test