[Pre537] Add success status response code check to lib/github_advisory_sync.rb for non-embedded URLs

[jasnow]

[Pre537] Add success status response code check to lib/github_advisory_sync.rb for non-embedded URLs

Currently best mitigation idea is to flag non-successful status response
codes and manually replace them from https://archive.org/web data.

FIelds involved are:
A. url:
B. related:/url:
C. Embedded to description: field (strength goal) (12/16/2026: Moved to #935)

[jasnow]

Now (see #936) I see that this issue is not planned so closing it.