fix bug when rendering rdv_upcoming_reminder mail
Created by: adipasquale
probably introduced with poorly named https://github.com/betagouv/rdv-solidarites.fr/commit/ace18322db884db668437e82ed026f002d9c8234
Created by: adipasquale
probably introduced with poorly named https://github.com/betagouv/rdv-solidarites.fr/commit/ace18322db884db668437e82ed026f002d9c8234