std: Rewrite vec_reserve_shared_actual in Rust

src/rt/rust_util.h

@@ -57,16 +57,6 @@ vec_data(rust_vec *v) {
     return reinterpret_cast<T*>(v->data);
 }
 
-inline void reserve_vec_exact_shared(rust_task* task, rust_vec_box** vpp,
-                                     size_t size) {
-    rust_opaque_box** ovpp = (rust_opaque_box**)vpp;
-    if (size > (*vpp)->body.alloc) {
-        *vpp = (rust_vec_box*)task->boxed.realloc(
-            *ovpp, size + sizeof(rust_vec));
-        (*vpp)->body.alloc = size;
-    }
-}
-
 inline void reserve_vec_exact(rust_vec_box** vpp,
                               size_t size) {
     if (size > (*vpp)->body.alloc) {