Remove redundant ST7735_BL variant defs.

No need for _V05 and _V03 definitions - I think there was a slight misunderstanding
on how variant files are supposed to _decrease_ #ifdef code in the cpp files.

src/main.cpp

@@ -280,15 +280,11 @@ void setup()
 
 #if defined(VEXT_ENABLE_V03)
     pinMode(VEXT_ENABLE_V03, OUTPUT);
-    pinMode(ST7735_BL_V03, OUTPUT);
     digitalWrite(VEXT_ENABLE_V03, 0); // turn on the display power and antenna boost
-    digitalWrite(ST7735_BL_V03, 1);   // display backligth on
     LOG_DEBUG("HELTEC Detect Tracker V1.0\n");
 #elif defined(VEXT_ENABLE_V05)
     pinMode(VEXT_ENABLE_V05, OUTPUT);
-    pinMode(ST7735_BL_V05, OUTPUT);
     digitalWrite(VEXT_ENABLE_V05, 1); // turn on the lora antenna boost
-    digitalWrite(ST7735_BL_V05, 1);   // turn on display backligth
     LOG_DEBUG("HELTEC Detect Tracker V1.1\n");
 #elif defined(VEXT_ENABLE) && defined(VEXT_ON_VALUE)
     pinMode(VEXT_ENABLE, OUTPUT);
@@ -1149,4 +1145,4 @@ void loop()
     }
     // if (didWake) LOG_DEBUG("wake!\n");
 }
-#endif
+#endif