[applets/batterymonitor] Fit it, pt.13: Hotfix CompactRepresentation

Xmas special.

Fixes the following error:

/usr/share/plasma/plasmoids/org.kde.plasma.battery/contents/ui/CompactRepresentation.qml:74:
ReferenceError: batteryLabel is not defined

batteryLabel does not exist ever since commit 27ac0b76 back in 2016, so an attempt to calculate some icon's height based on its size was bound to fail.

Before	After (% off)	After (% on)

Note, that "Before" the applet had "Show Battery Percentage on Icon" option set to OFF.