Add in delete propagations for publishing scripts

[mmcky]

currently we sync via update files only rules and don't propagate deletions as that is the default behaviour for aws cli s3 sync.

As lectures move between repositories this leaves behind stale html pages.

We need a mechanism to clean these up.

One option is to propagate deletions when sycning but we will need sphinx to build complete sites and sitemaps need to be added into the sync process

[mmcky]

Not required as moved to GitHub actions