refactor: modify regex group

LanguageRecogniser/Cpp/CppClassDiagramVisitor.cs

@@ -119,7 +119,7 @@ public class CppClassDiagramVisitor : CPP14ParserBaseVisitor<object>
                         Match aggregationMatch = Regex.Match(atribute.Type, aggregationPattern);
                         Match compositionMatch = Regex.Match(atribute.Type, compositionPattern);
 
-                        if (aggregationMatch.Success && !string.IsNullOrEmpty(aggregationMatch.Groups[2].Value))
+                        if (aggregationMatch.Success && !string.IsNullOrEmpty(aggregationMatch.Groups[3].Value))
                         {
                             // Aggregation type
                             string? typeName = aggregationMatch.Groups[2].Value; // Second capturing group