Remove ToolCallMessage struct from ChatData model

Author: Visual-Studio-Coder

Sources/Grok-API-SDK/Models/ChatData.swift

@@ -241,12 +241,4 @@ public struct SchemaDetails: Codable, Sendable {
 public struct SchemaProperty: Codable, Sendable {
     public let type: String
     public let description: String?
-}
-
-public struct ToolCallMessage: Codable, Sendable {
-    public let toolCalls: [ToolCall]?
-
-    enum CodingKeys: String, CodingKey {
-        case toolCalls = "tool_calls"
-    }
-}
+}