check: only show additional files if verbose output is enabled

Additional files are nearly always caused by interrupted backup runs.
This is unproblematic, thus don't pollute the check output with it.

cmd/restic/cmd_check.go

@@ -289,7 +289,7 @@ func runCheck(ctx context.Context, opts CheckOptions, gopts GlobalOptions, args
 		if errors.As(err, &packErr) {
 			if packErr.Orphaned {
 				orphanedPacks++
-				printer.P("%v\n", err)
+				printer.V("%v\n", err)
 			} else {
 				if packErr.Truncated {
 					salvagePacks.Insert(packErr.ID)