No address step before signing in when there's only one mail server

The server's own page asks for the username, so with a single server the
sign-in page keeps only the own-device choice. With several servers the
address still comes first, since its domain picks the server. One new string,
in all nine catalogues.

web/src/locales/fr.ts

@@ -1221,6 +1221,7 @@ export const catalog: Catalog = {
     "Could not send the receipt: {error}": "Impossible d’envoyer l’accusé de lecture : {error}",
     "Could not sign in.": "Connexion impossible.",
     "You'll enter your password on your mail server's sign-in page.": "Vous saisirez votre mot de passe sur la page de connexion de votre serveur de messagerie.",
+    "You'll sign in on your mail server's own page.": "Vous vous connecterez sur la page de votre serveur de messagerie.",
     "This sign-in didn't start in this browser. Try again.": "Cette connexion n’a pas commencé dans ce navigateur. Réessayez.",
     "The sign-in took too long. Try again.": "La connexion a pris trop de temps. Réessayez.",
     "Sign-in was cancelled.": "La connexion a été annulée.",