fix modifiers for various classes

Co-Authored-By: Taloth <Taloth@users.noreply.github.com>

src/NzbDrone.Core/Download/Clients/NzbVortex/NzbVortexAuthenticationException.cs

@@ -1,8 +1,8 @@
-using System;
+using System;
 
 namespace NzbDrone.Core.Download.Clients.NzbVortex
 {
-    internal class NzbVortexAuthenticationException : DownloadClientException
+    public class NzbVortexAuthenticationException : DownloadClientException
     {
         public NzbVortexAuthenticationException(string message, params object[] args)
             : base(message, args)

src/NzbDrone.Core/Download/Clients/NzbVortex/NzbVortexNotLoggedInException.cs

@@ -1,8 +1,8 @@
-using System;
+using System;
 
 namespace NzbDrone.Core.Download.Clients.NzbVortex
 {
-    internal class NzbVortexNotLoggedInException : DownloadClientException
+    public class NzbVortexNotLoggedInException : DownloadClientException
     {
         public NzbVortexNotLoggedInException()
             : this("Authentication is required")

src/NzbDrone.Core/Notifications/Discord/DiscordException.cs

@@ -3,7 +3,7 @@ using NzbDrone.Common.Exceptions;
 
 namespace NzbDrone.Core.Notifications.Discord
 {
-    internal class DiscordException : NzbDroneException
+    public class DiscordException : NzbDroneException
     {
         public DiscordException(string message)
             : base(message)

src/NzbDrone.Core/Notifications/Slack/SlackExeption.cs

@@ -1,9 +1,9 @@
-using System;
+using System;
 using NzbDrone.Common.Exceptions;
 
 namespace NzbDrone.Core.Notifications.Slack
 {
-    internal class SlackExeption : NzbDroneException
+    public class SlackExeption : NzbDroneException
     {
         public SlackExeption(string message)
             : base(message)

src/NzbDrone.Core/Notifications/Twitter/Twitter.cs

@@ -6,7 +6,7 @@ using NzbDrone.Core.Validation;
 
 namespace NzbDrone.Core.Notifications.Twitter
 {
-    internal class Twitter : NotificationBase<TwitterSettings>
+    public class Twitter : NotificationBase<TwitterSettings>
     {
         private readonly ITwitterService _twitterService;