Issue in /src/pages/guides/creating-python-plugin.md

I was going over the "Creating a Python plugin" tutorial, and had issues running the custom_import.py plugin code. It seems that PySide 2 is not supported in the most recent version of Substance Painter.

Is the following more appropriate? While I still had errors after making this change, at least it loaded the plugin.

from PySide6 import QtWidgets
from PySide6.QtGui import QAction

從 src/pages/guides/creating-python-plugin.md 開始，搭配報告中的 PySide2 和 PySide6 imports 檢視 custom_import.py 範例。確認目前的 Substance Painter 版本支援哪種 import 形式，然後更新教學，讓範例能在不出現報告中的 import 問題下載入。

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