py,st3m: overlays: Initialize battery percentage to 100 as an int

Otherwise it gets displayed as "100.0", and because value update is
guarded with equality check it doesn't fix itself until the percentage
gets down to 99%.

python_payload/st3m/ui/elements/overlays.py

@@ -560,7 +560,7 @@ class BatteryIcon(Icon):
 
     def __init__(self) -> None:
         super().__init__()
-        self._percent = 100.0
+        self._percent = 100
 
     def visible(self) -> bool:
         return power.has_battery