devel/electron21: update to 21.4.0

Changelog:

• https://github.com/electron/electron/releases/tag/v21.2.1
• https://github.com/electron/electron/releases/tag/v21.2.2
• https://github.com/electron/electron/releases/tag/v21.2.3
• https://github.com/electron/electron/releases/tag/v21.3.0
• https://github.com/electron/electron/releases/tag/v21.3.1
• https://github.com/electron/electron/releases/tag/v21.3.3
• https://github.com/electron/electron/releases/tag/v21.3.4
• https://github.com/electron/electron/releases/tag/v21.3.5
• https://github.com/electron/electron/releases/tag/v21.4.0