Log Message:
xfce4-power-manager: update to 4.18.1

Change log:

4.18.1 (2023-02-10)
======
- Update copyright year
- Use XfceScreensaver from Libxfce4ui (!33)
- screensaver: Fall back on lock command if D-Bus call failed (#142, !24)
- panel-plugin: Properly disconnect signal handler
- build: Fix autotools warnings
- Fix management of source ids
- panel-plugin: Add missing ref on image
- Fix blurriness in icons when UI scale factor > 1 (!30)
- Translation Updates:
  Chinese (China), English (Canada), Greek, Korean, Turkish