Implicit usings and more global usings

src/NadekoBot/Services/strings/impl/LocalFileStringsSource.cs

@@ -1,5 +1,4 @@
-using System.IO;
-using Newtonsoft.Json;
+using Newtonsoft.Json;
 using YamlDotNet.Serialization;
 
 namespace NadekoBot.Services;

src/NadekoBot/Services/strings/impl/RedisBotStringsProvider.cs

@@ -1,5 +1,4 @@
 using System.Web;
-using Discord.WebSocket;
 using NadekoBot.Extensions;
 using StackExchange.Redis;