cos/tools: Change the base image to debian:bookworm backports

There is an issue related to mem declare for kernels versions after 6.1.
Changing it to backports for the fix.

BUG=b/265997239
TEST=presubmit
RELEASE_NOTE=None

Change-Id: Ib7618fef7c0fac4ec490bf22e68fe7c0583c11db
Reviewed-on: https://cos-review.googlesource.com/c/cos/tools/+/42847
Reviewed-by: Meena Shanmugam <meenashanmugam@google.com>
Tested-by: Varsha Teratipally <teratipally@google.com>
Cloud-Build: GCB Service account <228075978874@cloudbuild.gserviceaccount.com>
diff --git a/src/cmd/cos_kdump_debugger/Dockerfile b/src/cmd/cos_kdump_debugger/Dockerfile
index f81c858..5792724 100644
--- a/src/cmd/cos_kdump_debugger/Dockerfile
+++ b/src/cmd/cos_kdump_debugger/Dockerfile
@@ -1,5 +1,5 @@
-# Start from debian
-FROM debian:bookworm
+# Start from ubuntu
+FROM debian:bookworm-backports
 
 RUN apt-get update