box: build fix

I got compile error for release build on gcc 14.2.1 20240910 version.

```
In function ‘char* mp_store_double(char*, double)’,
    inlined from ‘char* mp_encode_double(char*, double)’ at /home/shiny/dev/tarantool-ee/tarantool/src/lib/msgpuck/msgpuck.h:2409:24,
    inlined from ‘uint32_t tuple_hash_field(uint32_t*, uint32_t*, const char**, field_type, coll*)’ at /home/shiny/dev/tarantool-ee/tarantool/src/box/tuple_hash.cc:317:46:
/home/shiny/dev/tarantool-ee/tarantool/src/lib/msgpuck/msgpuck.h:340:16: error: ‘value’ may be used uninitialized [-Werror=maybe-uninitialized]
  340 |         cast.d = val;
      |         ~~~~~~~^~~~~
/home/shiny/dev/tarantool-ee/tarantool/src/box/tuple_hash.cc: In function ‘uint32_t tuple_hash_field(uint32_t*, uint32_t*, const char**, field_type, coll*)’:
/home/shiny/dev/tarantool-ee/tarantool/src/box/tuple_hash.cc:311:24: note: ‘value’ was declared here
  311 |                 double value;
      |
```

NO_TEST=build fix
NO_CHANGELOG=build fix
NO_DOC=build fix

(cherry picked from commit 1129c758d0e3bd86eec89e5229eac3f99155d8ac)