Tweak "can not" => "can't" in RUMBA pins

Marlin/pins_RUMBA.h

 #endif
 
 #if TEMP_SENSOR_2 == -1
-  #define TEMP_2_PIN        7   // Analog Input (connector *K3* on RUMBA thermocouple ADD ON is used <-- this can not be used when TEMP_SENSOR_BED is defined as thermocouple)
+  #define TEMP_2_PIN        7   // Analog Input (connector *K3* on RUMBA thermocouple ADD ON is used <-- this can't be used when TEMP_SENSOR_BED is defined as thermocouple)
 #else
   #define TEMP_2_PIN       13   // Analog Input (default connector for thermistor *T2* on rumba board is used)
 #endif
 //#define TEMP_X_PIN         12   // Analog Input (default connector for thermistor *T3* on rumba board is used)
 
 #if TEMP_SENSOR_BED == -1
-  #define TEMP_BED_PIN      7   // Analog Input (connector *K3* on RUMBA thermocouple ADD ON is used <-- this can not be used when TEMP_SENSOR_2 is defined as thermocouple)
+  #define TEMP_BED_PIN      7   // Analog Input (connector *K3* on RUMBA thermocouple ADD ON is used <-- this can't be used when TEMP_SENSOR_2 is defined as thermocouple)
 #else
   #define TEMP_BED_PIN     11   // Analog Input (default connector for thermistor *THB* on rumba board is used)
 #endif