fix(wio-tracker-l1): battery voltage reads high/jittery — divider always on

The per-read VBAT_ENABLE gating from 4d46abb2 (energy optimizations)
powered the battery voltage divider HIGH for only 10ms before each ADC
read, then LOW. 10ms is too short for the high-impedance divider node
to settle before the nRF52 SAADC samples it, so readings came out high
and inconsistent (e.g. 4.6-5.0V on a LiPo that maxes ~4.2V).

Hold VBAT_ENABLE HIGH continuously again (as before 4d46abb2) so the
node is always settled at sample time, and drop the toggle + delay(10)
from getBattMilliVolts(). Standby cost is ~2uA on the 2x1M divider,
negligible next to the device's mA-level draw.

The CPU-sleep and LED-off energy optimizations from 4d46abb2 are left
untouched — those are the real savings; only the VBAT gating is reverted.

variants/wio-tracker-l1/WioTrackerL1Board.cpp

@@ -9,7 +9,9 @@ void WioTrackerL1Board::begin() {
 
   pinMode(PIN_VBAT_READ, INPUT); // VBAT ADC input
   pinMode(VBAT_ENABLE, OUTPUT);
-  digitalWrite(VBAT_ENABLE, LOW); // keep voltage divider off; enabled only during ADC read
+  digitalWrite(VBAT_ENABLE, HIGH); // voltage divider always on: gating it per-read left
+                                   // the divider node unsettled at sample time (10ms was
+                                   // too short), reading high & jittery. ~2uA standby cost.
   // Set all button pins to INPUT_PULLUP
   pinMode(PIN_BUTTON1, INPUT_PULLUP);
   pinMode(PIN_BUTTON2, INPUT_PULLUP);