meson: bump minimum required Perl version to 5.26.0

meson: bump minimum required Perl version to 5.26.0

Commit 702d8c1f3b (Require Perl 5.26.0, 2024-10-23) dropped support
for Perl versions older than 5.26.0. The Meson build system, which
has been developed in parallel to that commit, hasn't been bumped
accordingly and thus still requires Perl 5.8.1 or newer.

Fix this by requiring Perl 5.26.0 or newer with Meson.

Signed-off-by: Peter Oliver <git@mavit.org.uk>
Reviewed-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>