Apply TERN to compact code (#17619)

Marlin/src/gcode/calibrate/M48.cpp

@@ -263,9 +263,7 @@ void GcodeSuite::M48() {
   restore_feedrate_and_scaling();
 
   // Re-enable bed level correction if it had been on
-  #if HAS_LEVELING
-    set_bed_leveling_enabled(was_enabled);
-  #endif
+  TERN_(HAS_LEVELING, set_bed_leveling_enabled(was_enabled));
 
   report_current_position();
 }