compact: remove cancel on SyncMetas errors (#5923)

in a favour of 86b4039 SyncMetas will retry if it's retriable.
Also, the cleanPartialMarked calls are surrounded by runutil.Repeat() will be repeated,
the ones not and are not retriable will throw an interrupt to run.Group() by returning err
and Group will call cancel() as it's configured for its interrupt func.

Signed-off-by: Seena Fallah <seenafallah@gmail.com>

Signed-off-by: Seena Fallah <seenafallah@gmail.com>

cmd/thanos/compact.go

@@ -406,7 +406,6 @@ func runCompact(
 		defer cleanMtx.Unlock()
 
 		if err := sy.SyncMetas(ctx); err != nil {
-			cancel()
 			return errors.Wrap(err, "syncing metas")
 		}