Switch SP6+ to public-dl.suse.com

We'll move installer-updates to a fixed-ip setup to maximize
interoperability. However BCI should use the direct CDN link, so switch
to that.

bci_tester/data.py

@@ -222,7 +222,7 @@ def create_container_version_mark(
         BCI_DEVEL_REPO = "http://download.opensuse.org/tumbleweed/repo/oss/"
     else:
         # from SLE 15 SP6 onward we use the unauthenticated CDN
-        cdn_prefix = "installer-updates" if OS_SP_VERSION >= 6 else "updates"
+        cdn_prefix = "public-dl" if OS_SP_VERSION >= 6 else "updates"
         BCI_DEVEL_REPO = f"https://{cdn_prefix}.suse.com/SUSE/Products/SLE-BCI/{OS_MAJOR_VERSION}-SP{OS_SP_VERSION}/{LOCALHOST.system_info.arch}/product/"
     _BCI_REPLACE_REPO_CONTAINERFILE = ""
 else: