misc: 清除冗余的代码

Reviewed-on: PostGuard/Canon#75
Co-authored-by: Lan_G <2911328695@qq.com>
Co-committed-by: Lan_G <2911328695@qq.com>

Canon.Core/CodeGenerators/CCodeBuilder.cs

@@ -1,5 +1,4 @@
 using System.Text;
-using Canon.Core.SemanticParser;
 
 namespace Canon.Core.CodeGenerators;
 
@@ -13,11 +12,6 @@ public class CCodeBuilder
     private int _scopeCount = 0;
     private string _scopeEmpty = string.Empty;
 
-    public void AddString(string code)
-    {
-        _builder.Append(code);
-    }
-
     public void AddLine(string code)
     {
         foreach (string line in code.Split('\n'))