pageserver: ignore CollectKeySpaceError::Cancelled during compaction (#10968)

This pops up a few times during deployment. Not sure why it fires
without `self.cancel` being cancelled, but could be e.g. ancestor
timelines or sth.

pageserver/src/tenant/timeline/compaction.rs

@@ -779,6 +779,7 @@ impl Timeline {
             // Suppress errors when cancelled.
             Err(_) if self.cancel.is_cancelled() => {}
             Err(CompactionError::ShuttingDown) => {}
+            Err(CompactionError::CollectKeySpaceError(CollectKeySpaceError::Cancelled)) => {}
 
             // Alert on critical errors that indicate data corruption.
             Err(