Move unlock call to a background context in GC

This ensures that if the GC operation times out, the unlock still can run

internal/datastore/common/gc.go

@@ -196,7 +196,7 @@ func RunGarbageCollection(gc GarbageCollector, window, timeout time.Duration) er
 	}
 
 	defer func() {
-		err := gc.UnlockAfterGCRun(ctx)
+		err := gc.UnlockAfterGCRun(context.Background())
 		if err != nil {
 			log.Error().
 				Err(err).