fix(preload): Fix bad merge in ECG app

OFFSET was renamed to OFFSET_Y in ea5a30d9 ("add pause-mode"), while
the call to `draw_leds()` in bc7e3b92 ("Add led activity to ECG app")
still uses the old name. This causes an exception and the ECG app fails
to proceed past the start screen.
2 jobs for !269 with patch-1 in 1 minute and 4 seconds (queued for 4 seconds)
merge request