[DOC] Fix typo in gc/default.c

gc/default.c

@@ -3726,7 +3726,7 @@ gc_sweep_plane(rb_objspace_t *objspace, rb_heap_t *heap, uintptr_t p, bits_t bit
                         obj_free_object_id(objspace, vp);
                     }
                     // always add free slots back to the swept pages freelist,
-                    // so that if we're comapacting, we can re-use the slots
+                    // so that if we're compacting, we can re-use the slots
                     (void)VALGRIND_MAKE_MEM_UNDEFINED((void*)p, BASE_SLOT_SIZE);
                     heap_page_add_freeobj(objspace, sweep_page, vp);
                     gc_report(3, objspace, "page_sweep: %s is added to freelist\n", rb_obj_info(vp));