Simplify the lightbox image caption

[nimmolo]

To remove extra queries on the obs index.

To reproduce the issue, on <main> go to http://localhost:3000/505457, and then hit "Index" to be sure we're on the same page of the index. Extra queries will fire after the line

  Rendered application/content/_sorter.html.erb (Duration: 0.2ms | Allocations: 172)

If you examine the lightbox caption for observations like 505457 (it's encoded as a data-attribute in the image) you'll find the ID's of some of the associations that are firing the extra queries.

The issue is compounded on the matrix-box carousel PR #1598 because every image in every matrix box gets a lightbox caption.

Note that changes in this PR will also affect lightboxes on the show_obs page. This PR:

• Replaces the lightbox caption's use of show_obs_title, which has links to owner namings, deprecated names etc., and uses the shorter matrix-box-style obs name instead, linking to the obs.
• Provisionally eliminates the obs notes from the lightbox caption, because it's the only place i could think that might involve projects. These were some of the extra associations getting loaded. Please let me know if that's not the case. It could be the image copyright instead, for example.

Restored the obs notes because I believe the title was causing all the problems.

[coveralls]

Changes unknown when pulling c4c39b3 on nimmo-simplify-lightbox-caption into ** on main**.