Make it mandatory for the user to set the master fingerprint in the wallet settings for seed signing. Improve error messages.

BTCPayServer.Tests/SeleniumTests.cs

@@ -485,8 +485,6 @@ namespace BTCPayServer.Tests
                     }
                 }
                 SignWith(mnemonic);
-                var accountKey = root.Derive(new KeyPath("m/84'/1'/0'")).GetWif(Network.RegTest).ToString();
-                SignWith(accountKey);
             }
         }
     }