t8002: fix ambiguous printf conversion specifications

t8002: fix ambiguous printf conversion specifications

In e7fb2ca945 (builtin/blame: fix out-of-bounds write with blank
boundary commits, 2025-01-10), we have introduced two new tests that
expect a certain amount of padding. This padding is generated via
printf using the "%0.s" conversion specification. That directive is
ambiguous because it might be interpreted as field width (most shells)
or 0-padding flag for numeric fields (coreutils).

Fix this issue by using "%${N}s" instead, which is already being
used in other tests (i.e. t5300, t0450) and is unambiguous.

Helped-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Jan Palus <jpalus@fastmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>