Removed dead code

FitConnect/JsonSchemas/JsonSchemaSettings.cs

-namespace FitConnect.JsonSchemas; 
-
-public class JsonSchemaSettings {
-    public const string SetSchema =
-        "https://schema.fitko.de/fit-connect/set-payload/1.0.1/set-payload.schema.json";
-}

FitConnect/Models/SET/SecurityEventToken.cs

 using System.Security.Claims;
 using FitConnect.Encryption;
-using FitConnect.JsonSchemas;
 using FitConnect.Models.v1.Api;
 using IdentityModel;
 using Microsoft.IdentityModel.JsonWebTokens;
 using Microsoft.IdentityModel.Tokens;
 using Newtonsoft.Json;
 using Newtonsoft.Json.Linq;
-using NJsonSchema;
 
 namespace FitConnect.Models;