Fix Chatter 2 blank screen on boot (#4759)

As reported by @eureekasigns and @GPSFan, Chatter 2 had begun
to show a blank screen on boot after recent TFT display changes.

Setting TFT_BACKLIGHT_ON LOW resolves the issue.

Fixes https://github.com/meshtastic/firmware/issues/4751

variants/chatter2/variant.h

@@ -66,6 +66,7 @@
 #define SCREEN_ROTATE
 #define SCREEN_TRANSITION_FRAMERATE 5 // fps
 #define DISPLAY_FORCE_SMALL_FONTS
+#define TFT_BACKLIGHT_ON LOW
 
 // Battery
 
@@ -121,4 +122,4 @@
 // cannot serve any extra function even if requested to LORA_DIO3 value is never used in src (as we are not using RF95), so no
 // need to define, and DIO3_AS_TCXO_AT_1V8 is set so it cannot serve any extra function even if requested to (from 13.3.2.1
 // DioxMask in SX1262 datasheet: Note that if DIO2 or DIO3 are used to control the RF Switch or the TCXO, the IRQ will not be
-// generated even if it is mapped to the pins.)
+// generated even if it is mapped to the pins.)