Use a proper client for fetch byte

pkg/realdebrid/api.go

@@ -296,7 +296,7 @@ func (rd *RealDebrid) UnrestrictLink(link string) (*UnrestrictResponse, error) {
 		return nil, fmt.Errorf("undecodable response so likely it has expired")
 	}
 
-	if !canFetchFirstByte(response.Download) {
+	if !rd.canFetchFirstByte(response.Download) {
 		return nil, fmt.Errorf("can't fetch first byte")
 	}