Update LED_BUILTIN in pins_arduino.h for esp32c3.

According to this manual:
https://wiki.icbbuy.com/doku.php?id=developmentboard:esp32-c3mini.
Also, I checked it myself on my esp32c3.

Author: stan220

variants/esp32c3/pins_arduino.h

@@ -6,7 +6,7 @@
 
 #define PIN_NEOPIXEL 8
 // BUILTIN_LED can be used in new Arduino API digitalWrite() like in Blink.ino
-static const uint8_t LED_BUILTIN = SOC_GPIO_PIN_COUNT + PIN_NEOPIXEL;
+static const uint8_t LED_BUILTIN = PIN_NEOPIXEL;
 #define BUILTIN_LED LED_BUILTIN  // backward compatibility
 #define LED_BUILTIN LED_BUILTIN  // allow testing #ifdef LED_BUILTIN
 // RGB_BUILTIN and RGB_BRIGHTNESS can be used in new Arduino API neopixelWrite()