esp32: fix 4.x pin detach argument

Author: zachwelch

src/esp32/Servo.cpp

@@ -48,7 +48,7 @@ class ServoImpl {
 
     ~ServoImpl() {
 #if ESP_IDF_VERSION_MAJOR < 5
-      ledcDetachPin(channel);
+      ledcDetachPin(pin);
 #else
       ledcDetach(pin);
 #endif