Fix Z_STEPPER_ALIGN_[XY] sanity error (#15124)

Marlin/src/inc/SanityCheck.h

   constexpr float sanity_arr_z_align_x[] = Z_STEPPER_ALIGN_X, sanity_arr_z_align_y[] = Z_STEPPER_ALIGN_Y;
   static_assert(
     COUNT(sanity_arr_z_align_x) == Z_STEPPER_COUNT && COUNT(sanity_arr_z_align_y) == Z_STEPPER_COUNT,
-    "Z_STEPPER_ALIGN_[XY]POS settings require one element per Z stepper."
+    "Z_STEPPER_ALIGN_[XY] settings require one element per Z stepper."
   );
 #endif