turn off 3.3v rail when powering off

variants/lilygo_t_impulse_plus/TImpulsePlusBoard.h

@@ -48,6 +48,12 @@ public:
   }
 
   void powerOff() override {
+
+    // turn off 3.3v
+    digitalWrite(RT9080_EN, LOW);
+
+    // power off system
     sd_power_system_off();
+
   }
 };