Fix build (7.2) CI failure: point apt to archive.debian.org for EOL buster

[Copilot]

The build (7.2) CI job failed because php:7.2 is built on Debian buster, which reached EOL and was pulled from the live deb.debian.org/security.debian.org mirrors (404 on apt-get update).

Changes

• ci/Dockerfile: before apt-get update, detect buster via /etc/os-release and rewrite /etc/apt/sources.list to use archive.debian.org instead of the live mirrors.
• Scoped to buster only, so other matrix versions (7.3, 7.4, 8.0, 8.1, 8.2.0beta2) build against their current (non-EOL) Debian codenames unaffected.

RUN if grep -q buster /etc/os-release 2>/dev/null; then \
        sed -i \
            -e 's|deb.debian.org/debian|archive.debian.org/debian|g' \
            -e 's|security.debian.org/debian-security|archive.debian.org/debian-security|g' \
            /etc/apt/sources.list; \
    fi \
    && apt-get update && apt-get install -y unzip && apt-get clean

[Raymond Zhao (rzhao271)]

Copilot Remove the workflow instead considering it has reached EOL.

[Copilot]

Copilot Remove the workflow instead considering it has reached EOL.

Done in 71fadea — reverted the apt-source workaround in ci/Dockerfile and removed PHP 7.2 from the CI matrix in .github/workflows/main.yml.