fix(about_dialog): Always use black color for window texts

[siketyan]

Description

Updated the QPalette in AboutDialog.app to display texts in black colour even if dark mode is enabled on the environment.

I am really noob of Qt/C++ stack; please let me know if I am missing something to do or doing wrong.

Issue IDs

Closes #897

Steps to test new behaviors (if any)

• OS: Any environment that dark mode is supported by Qt
• Steps:
  1. Open the about dialog
  2. Confirm that texts in the window is written in black color

Before	After

Additional context

Tested on macOS 14.4 Sonoma, Arm64, M1 Max, Mac Studio (2022).

[hiroyuki-komatsu]

Hi siketyan,

We have been running the internal process to accept your PR. Thank you for your contribution.

[hiroyuki-komatsu]

We have merged your PR. Thank you for the contribution!