BDF : update data more frequently

As reported by a user, there is a systematic lag between daily data provided Webstat and data provided by DBnomics. For example, compare webstat.banque-france.fr/fr/quickview.do?SERIES_KEY=248.EXR.D.USD.EUR.SP00.A and https://db.nomics.world/BDF/EXR/EXR.D.USD.EUR.SP00.A