Correct analog sampling time for additional A to D sample

Adjusted the  #define PID_dT to reflect 10 A to D sample steps, vs
original 8.

Marlin/Configuration.h

@@ -185,7 +185,7 @@
                                   // is more then PID_FUNCTIONAL_RANGE then the PID will be shut off and the heater will be set to min/max.
   #define PID_INTEGRAL_DRIVE_MAX 255  //limit for the integral term
   #define K1 0.95 //smoothing factor within the PID
-  #define PID_dT ((OVERSAMPLENR * 8.0)/(F_CPU / 64.0 / 256.0)) //sampling period of the temperature routine
+  #define PID_dT ((OVERSAMPLENR * 10.0)/(F_CPU / 64.0 / 256.0)) //sampling period of the temperature routine
 
 // If you are using a pre-configured hotend then you can use one of the value sets by uncommenting it
 // Ultimaker