notes tests: don't ignore "git" exit code

notes tests: don't ignore "git" exit code

Change a fragile test pattern that's been with us ever since these
tests were introduced in [1], [2] and [3] to properly return the exit
code of the failing command on failure.

Because of this I'd marked this test as passing under SANITIZE=leak in
[4] and [5]. We need to remove those annotations as these tests will
no longer pass.

1. 9081a421a6d (checkout: fix "branch info" memory leaks, 2021-11-16)
2. 0057c0917d3 (Add selftests verifying that we can parse notes trees
   with various fanouts, 2009-10-09)
3. 048cdd4665e (t3305: Verify that adding many notes with git-notes
   triggers increased fanout, 2010-02-13)
4. ca089724952 (leak tests: mark some notes tests as passing with
   SANITIZE=leak, 2021-10-31)
5. 9081a421a6d (checkout: fix "branch info" memory leaks, 2021-11-16)

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