lint: refactor SlowMode -> SlowModeInterval

this was the name change i always wanted

src/Discord.Net.Core/Entities/Channels/ITextChannel.cs

@@ -14,7 +14,7 @@ namespace Discord
         string Topic { get; }
 
         ///<summary> Gets the current slow-mode delay for this channel. 0 if disabled. </summary>
-        int SlowMode { get; }
+        int SlowModeInterval { get; }
 
         /// <summary> Bulk deletes multiple messages. </summary>
         Task DeleteMessagesAsync(IEnumerable<IMessage> messages, RequestOptions options = null);

src/Discord.Net.Core/Entities/Channels/TextChannelProperties.cs

@@ -22,6 +22,6 @@ namespace Discord
         /// Users with <see cref="ChannelPermission.ManageMessages"/> will be exempt from slow-mode.
         /// </remarks>
         /// <exception cref="ArgumentOutOfRangeException">Throws ArgummentOutOfRange if the value does not fall within [0, 120]</exception>
-        public Optional<int> SlowMode { get; set; }
+        public Optional<int> SlowModeInterval { get; set; }
     }
 }