Remove distro specific run lines when converting

I see a lot of dockerfiles with these types of RUN statements:

# Generate the APT cache
# ENV DEBIAN_FRONTEND=noninteractive

# Add proxy
RUN echo deb [trusted=yes] https://<host>/repository/apt-proxy-12/ bookworm main contrib non-free > /etc/apt/sources.list
RUN echo deb-src [trusted=yes] https://<host>/repository/apt-proxy-12/ bookworm main contrib non-free >> /etc/apt/sources.list

RUN echo deb [trusted=yes] https://<host>/repository/apt-proxy-12/ bookworm-updates main contrib non-free >> /etc/apt/sources.list
RUN echo deb-src [trusted=yes] https://<host>/repository/apt-proxy-12/ bookworm-updates main contrib non-free >> /etc/apt/sources.list

RUN echo deb [trusted=yes] https://<host>/repository/apt-proxy-12/ bookworm-proposed-updates main contrib non-free >> /etc/apt/sources.list
RUN echo deb-src [trusted=yes] https://<host>/repository/apt-proxy-12/ bookworm-proposed-updates main contrib non-free >> /etc/apt/sources.list

It would be nice if DFC could recognize these and either comment them out or remove them

The issue names no files or tests; start by locating DFC's Dockerfile conversion logic for RUN instructions and reproduce the APT/proxy example. Done means conversion recognizes these distro-specific RUN lines and consistently comments them out or removes them, with a regression check for the shown patterns.