fix/array file cannot use in iteration node (#12035)

Signed-off-by: -LAN- <laipz8200@outlook.com>

api/core/variables/variables.py

     pass
 
 
-class ArrayFileVariable(ArrayFileSegment, Variable):
+class ArrayFileVariable(ArrayFileSegment, ArrayVariable):
     pass

api/tests/unit_tests/core/app/segments/test_variables.py

 from pydantic import ValidationError
 
 from core.variables import (
+    ArrayFileVariable,
+    ArrayVariable,
     FloatVariable,
     IntegerVariable,
     ObjectVariable,
     assert var.to_object() == 3.14
     var = SecretVariable(name="secret", value="secret_value")
     assert var.to_object() == "secret_value"
+
+
+def test_array_file_variable_is_array_variable():
+    var = ArrayFileVariable(name="files", value=[])
+    assert isinstance(var, ArrayVariable)