Update Servo.cpp

Updated "servo.h" to "Servo.h"

Marlin/Servo.cpp

 #include <avr/interrupt.h>
 #include <Arduino.h>
 
-#include "servo.h"
+#include "Servo.h"
 
 #define usToTicks(_us)    (( clockCyclesPerMicrosecond()* _us) / 8)     // converts microseconds to tick (assumes prescale of 8)  // 12 Aug 2009
 #define ticksToUs(_ticks) (( (unsigned)_ticks * 8)/ clockCyclesPerMicrosecond() ) // converts from ticks back to microseconds