Remove dead rb_darray_swap_remove

Author: peterzhu2118

darray.h

@@ -73,20 +73,6 @@
     (*(ptr_to_ary))->meta.size++; \
 } while (0)
 
-/* Removes the element at idx and replaces it with the last element.
- * ptr_to_ary and idx is evaluated multiple times.
- * Warning: not bounds checked.
- *
- * void rb_darray_swap_remove(rb_darray(T) *ptr_to_ary, size_t idx);
- */
-#define rb_darray_swap_remove(ptr_to_ary, idx) do { \
-    size_t _darray_size = rb_darray_size(*(ptr_to_ary)); \
-    if ((idx) != _darray_size - 1) { \
-        (*(ptr_to_ary))->data[idx] = (*(ptr_to_ary))->data[_darray_size - 1]; \
-    } \
-    (*(ptr_to_ary))->meta.size--; \
-} while (0)
-
 // Iterate over items of the array in a for loop
 //
 #define rb_darray_foreach(ary, idx_name, elem_ptr_var) \