Remove unneeded statement in `SET_OBJ_VALUE` with `boxing_word.h`
`(r).value.bp` and `v` have the same value due to assignment of the line
preceding the removed line.
@@ -141,7 +141,6 @@ mrb_type(mrb_value o)
#define SET_OBJ_VALUE(r,v) do { \
(r).w = 0; \
(r).value.p = (v); \
- if ((r).value.bp) (r).value.bp->tt = ((struct RObject*)(v))->tt; \
} while (0)
#endif /* MRUBY_BOXING_WORD_H */
