fix sed

Author: tgross35

ci/docker/x86_64-unknown-linux-gnu/Dockerfile

@@ -1,9 +1,10 @@
 FROM ubuntu:24.10
 
-RUN sed -i -re 's/([a-z]{2}\.)?archive.ubuntu.com|security.ubuntu.com/old-releases.ubuntu.com/g' /etc/apt/sources.list
+RUN sed -i 's|ports.ubuntu.com/ubuntu-ports/|old-releases.ubuntu.com/ubuntu/|g' \
+    /etc/apt/sources.list.d/ubuntu.sources
 RUN apt-get update
 RUN apt-get install -y --no-install-recommends \
-  gcc g++ libc6-dev ca-certificates linux-headers-generic
+    gcc g++ libc6-dev ca-certificates linux-headers-generic
 
 RUN apt search linux-headers
 RUN ls /usr/src