Update Helix 'led_test' keymap (#3292)

* now helix led_test local rgblight.[ch] not use. remove.

* greatly simplify keyboards/helix/rev2/keymaps/led_test/keymap.c

Helix keymap 'led_test' use modified default/keymap.c

keyboards/helix/rev2/keymaps/default/keymap.c

@@ -510,7 +510,14 @@ void music_scale_user(void)
 //SSD1306 OLED update loop, make sure to add #define SSD1306OLED in config.h
 #ifdef SSD1306OLED
 
+// hook point for 'led_test' keymap
+//   'default' keymap's led_test_init() is empty function, do nothing
+//   'led_test' keymap's led_test_init() force rgblight_mode_noeeprom(35);
+__attribute__ ((weak))
+void led_test_init(void) {}
+
 void matrix_scan_user(void) {
+     led_test_init();
      iota_gfx_task();  // this is what updates the display continuously
 }