Follow-up the PR #4860 (Fix BLTOUCH string and SERVO_DELAY)

Marlin/language_en.h

 #ifndef MSG_ZPROBE_OUT
   #define MSG_ZPROBE_OUT                      "Z probe out. bed"
 #endif
-#ifndef MSG_BLTOUCH_RESET
+#ifndef MSG_BLTOUCH_SELFTEST
   #define MSG_BLTOUCH_SELFTEST                "BLTouch Self-Test"
 #endif
 #ifndef MSG_BLTOUCH_RESET