Corrects typo in attribute name

Author: kevwhitt-hee

DigitalLearningSolutions.Web/Helpers/ExternalApis/TableauConnectionHelper.cs

@@ -42,7 +42,7 @@ public string GetTableauJwt(string email)
                 { "exp", new DateTimeOffset(DateTime.UtcNow.AddMinutes(5)).ToUnixTimeSeconds() },
                 { "sub", user },
                 { "scp", new[] { "tableau:views:embed" } },
-                { "ExernalUserEmail", new [] { email } }
+                { "ExternalUserEmail", email }
         };
             var token = new JwtSecurityToken(header, payload);
             var tokenHandler = new JwtSecurityTokenHandler();