Add a Z raise-between-probes to G34 (#13791)

Marlin/src/gcode/calibrate/G34_M422.cpp

@@ -126,6 +126,12 @@ void GcodeSuite::G34() {
       extruder_duplication_enabled = false;
     #endif
 
+    // Before moving other axes raise Z, if needed. Never lower Z.
+    if (current_position[Z_AXIS] < Z_CLEARANCE_BETWEEN_PROBES) {
+      if (DEBUGGING(LEVELING)) DEBUG_ECHOLNPAIR("Raise Z (before moving to probe pos) to ", Z_CLEARANCE_BETWEEN_PROBES);
+      do_blocking_move_to_z(Z_CLEARANCE_BETWEEN_PROBES);
+    }
+
     // Remember corrections to determine errors on each iteration
     float last_z_align_move[Z_STEPPER_COUNT] = ARRAY_N(Z_STEPPER_COUNT, 10000.0f, 10000.0f, 10000.0f),
           z_measured[Z_STEPPER_COUNT] = { 0 };