Fix host_response_handler debug

Marlin/src/feature/host_actions.cpp

 
   void host_response_handler(const uint8_t response) {
     #ifdef DEBUG_HOST_ACTIONS
-      SERIAL_ECHOLNPAIR("M86 Handle Reason: ", host_prompt_reason);
-      SERIAL_ECHOLNPAIR("M86 Handle Response: ", response);
+      SERIAL_ECHOLNPAIR("M876 Handle Reason: ", host_prompt_reason);
+      SERIAL_ECHOLNPAIR("M876 Handle Response: ", response);
     #endif
     const char *msg = PSTR("UNKNOWN STATE");
     const PromptReason hpr = host_prompt_reason;