xfce4-power-manager: update to 1.6.5

Change log:

1.6.5
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- Improve size of critical power level spin
- Correctly hide brightness label (Bug #14649)
- Replace GtkStock buttons
- Add icons to close and help buttons in prefs
- Translation Updates: Galician, Norwegian Bokm奪l, Portuguese (Brazil)

1.6.4
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- Make inhibition affect dimming and inactivity action (Bug #14687)
- Add support of xfce4-screensaver
- Disable trayicon when panel plugin is present (Bug #15682)
- Translation Updates:
  Armenian (Armenia), Finnish, Galician, Lithuanian, Norwegian Bokm奪l,
  Ukrainian

(gutteridge)