[Bug] Nested arrays decoding not working as expected

### Version
OS: Ubuntu 22.04
Python: 3.10.2
Pulsar: pulsar-client==3.2.0

### Minimal reproduce step
```python3
from pulsar.schema import JsonSchema, Record, Array, String

class A(Record):
a = String()

class B(Record):
b = Array(Array(A()))

# Decode JSON data
json_data = '{"b": [[{"a": "hello world"}]]}'
decoded_data = JsonSchema(B).decode(json_data)

# Access the nested objects
nested_objects = decoded_data.b[0][0]
print(type(nested_objects))
print(nested_objects.a)
```

### What did you expect to see?
```
<__main__.A object at 0x7fd1ecd07d00>
hello world
```

### What did you see instead?
```

Traceback (most recent call last):
File "", line 1, in
AttributeError: 'dict' object has no attribute 'a'
```

先使用 JsonSchema(B).decode 執行 Python 重現程式，並檢查巢狀的 Array 值如何解碼。追蹤 JsonSchema.decode 進入點，並新增涵蓋 Array(Array(A())); 的迴歸測試；當內部值是其 a 屬性設為 "hello world" 的 A 物件時，即完成。

由索引模型根據 Issue 內容生成。