hack: Drop skip_if_unavailable from COPR repo definitions

Both COPR repos (rhcontainerbot/bootc and @CoreOS/continuous) had
skip_if_unavailable=True, which caused a subtle failure mode: a
transient 502 on repomd.xml would cause dnf to silently skip the
repo, leaving $bootupd_nevra empty, and the subsequent
'dnf install $bootupd_nevra' would fail with the confusing error
'the following arguments are required: PACKAGE' rather than a clear
COPR unavailability message.

Without skip_if_unavailable the 502 fails fast and visibly, making
flaky CI failures from transient COPR outages much easier to diagnose.
COPR is either available or it isn't; silently skipping it just
defers the failure to a harder-to-read error.

Assisted-by: OpenCode (claude-sonnet-4-6)
Signed-off-by: Colin Walters <walters@verbum.org>

Author: cgwalters

hack/provision-derived.sh

@@ -86,7 +86,6 @@ cat >/etc/yum.repos.d/rhcontainerbot-bootc.repo <<REPOEOF
 name=Copr repo for bootc owned by rhcontainerbot
 baseurl=https://download.copr.fedorainfracloud.org/results/rhcontainerbot/bootc/${copr_distro}-\$releasever-\$basearch/
 type=rpm-md
-skip_if_unavailable=True
 gpgcheck=1
 gpgkey=https://download.copr.fedorainfracloud.org/results/rhcontainerbot/bootc/pubkey.gpg
 repo_gpgcheck=0
@@ -100,7 +99,6 @@ cat >/etc/yum.repos.d/coreos-continuous.repo <<REPOEOF
 name=Copr repo for continuous owned by @CoreOS
 baseurl=https://download.copr.fedorainfracloud.org/results/@CoreOS/continuous/${copr_distro}-\$releasever-\$basearch/
 type=rpm-md
-skip_if_unavailable=True
 gpgcheck=1
 gpgkey=https://download.copr.fedorainfracloud.org/results/@CoreOS/continuous/pubkey.gpg
 repo_gpgcheck=0