[GSoC] t2004: use test_path_is_file instead of test -f #26564

Job	Run time
config	6s
fuzz smoke test	1m 6s
win build	5m 26s
sparse	3m 29s
win+Meson build	5m 40s
documentation	7m 19s
static-analysis	5m 20s
osx-clang (macos-14)	14m 12s
osx-reftable (macos-14)	14m 11s
osx-gcc (macos-14)	14m 7s
osx-meson (macos-14)	13m 55s
rust-analysis	1m 55s
linux-musl-meson (alpine:latest)	8m 14s
linux-breaking-changes (ubuntu:rolling)	12m 58s
linux-meson (ubuntu:rolling)	13m 32s
linux-sha256 (ubuntu:rolling)	12m 34s
linux-TEST-vars (ubuntu:20.04)	13m 25s
fedora-breaking-changes-meson (fedora:latest)	9m 52s
debian-11 (debian:11)	10m 18s
linux-leaks (ubuntu:rolling)	13m 41s
win+VS build	0s
almalinux-8 (almalinux:8)	10m 21s
linux-reftable (ubuntu:rolling)	11m 43s
linux-reftable-leaks (ubuntu:rolling)	13m 41s
linux32 (i386/ubuntu:focal)	8m 19s
linux-asan-ubsan (ubuntu:rolling)	10m 9s
win+VS test	0s
win test (2)	8m 26s
win test (8)	6m 14s
win test (5)	6m 14s
win test (3)	6m 10s
win test (0)	9m 33s
win test (6)	6m 6s
win test (9)	9m 52s
win test (4)	8m 10s
win test (7)	6m 48s
win test (1)	6m 55s
win+Meson test (3)	32s
win+Meson test (2)	32s
win+Meson test (9)	34s
win+Meson test (5)	29s
win+Meson test (4)	35s
win+Meson test (7)	33s
win+Meson test (0)	41s
win+Meson test (6)	31s
win+Meson test (8)	34s
win+Meson test (1)	26s
	5h 15m 28s

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