Use replicated CVars for max chat message length.

Content.Shared/CCVar/CCVars.cs

@@ -345,5 +345,12 @@ namespace Content.Shared.CCVar
 
         public static readonly CVarDef<bool> ViewportScaleRender =
             CVarDef.Create("viewport.scale_render", true, CVar.CLIENTONLY | CVar.ARCHIVE);
+
+        /*
+         * CHAT
+         */
+
+        public static readonly CVarDef<int> ChatMaxMessageLength =
+            CVarDef.Create("chat.max_message_length", 1000, CVar.SERVER | CVar.REPLICATED);
     }
 }

Content.Shared/Chat/ChatMaxMsgLengthMessage.cs

@@ -1,29 +0,0 @@
-using Lidgren.Network;
-using Robust.Shared.Network;
-
-namespace Content.Shared.Chat
-{
-    /// <summary>
-    /// This message is sent by the server to let clients know what is the chat's character limit for this server.
-    /// It is first sent by the client as a request
-    /// </summary>
-    public sealed class ChatMaxMsgLengthMessage : NetMessage
-    {
-        public override MsgGroups MsgGroup => MsgGroups.Command;
-
-        /// <summary>
-        /// The max length a player-sent message can get
-        /// </summary>
-        public int MaxMessageLength { get; set; }
-
-        public override void ReadFromBuffer(NetIncomingMessage buffer)
-        {
-            MaxMessageLength = buffer.ReadInt32();
-        }
-
-        public override void WriteToBuffer(NetOutgoingMessage buffer)
-        {
-            buffer.Write(MaxMessageLength);
-        }
-    }
-}