make-container-image: revert to mediawiki-httpd
The mediawiki-httpd images are now rebased on bookworm, and thus equivalent to the transitional "-bookworm" track images.
Before those are retired, we need to switch image builds back to using the "plain" httpd images.
Note I've intentionally kept the -bookworm suffix in the flavour name, since it's an idiom that (IMO) will make the next transition clearer.
This is also analogous to what we've adopted for app images (-81).
Bug: T378128