Remove missing items from the itemsAPI response

[agnesgaroux]

Here

catalogue-api/items/src/main/scala/weco/api/items/services/SierraItemUpdater.scala

Line 75 in dc94db5

case Left(

When we get (a) missing item(s) in the Sierra response, we simply ignore them and deal only with the returned items, updating their AccessConditions
We then use the original itemsMap

catalogue-api/items/src/main/scala/weco/api/items/services/SierraItemUpdater.scala

Line 117 in dc94db5

updatedItems = itemMap.map {

to update the AccessConditions. Missing items are still in there, when they should be removed
See Slack convo with Collection Info https://wellcome.slack.com/archives/CGXDT2GSH/p1709290864376589