Contours for some manually uploaded events don't have matching skymap fits files in the cache

[niyuanqi]

Scope

Only affects some of the events that are manually uploaded. Events that are now automatically injected by gwtm_cron should not have the issue (see below). There's no imminent need to fix it because

1. The issue is limited to manually ingested past events (before updates made to gwtm_cron), and should not affect current or future events.
2. Skymap fits files are not currently used on the main event page, and are only ever used when operating the calculators (e.g., coverage calculator, renorm skymap; mainly important for current events, not past ones).

Can fix later if someone has time.

Description of bug with test case (240422ed)

Tried to generate 90/50 contours from the file "fit/S240422ed-Update.fits.gz" using ligo.skymap.postprocess.contour, expecting to reproduce the contours shown on the event page (see attached left image) under the "Update 2024-04-23 02:38:38.822226" tab. However, the contours I got from this file seemed to be slightly different (see attached right image), while they exactly match the ones shown under either one of the "Preliminary 12024-04-22 21:35:39" or "Initial 2024-04-22 21:35:39" tabs. Thus, it seems like the cached skymap files don't match the corresponding contours.