message: Fix query return type in migration guide
diff: @@ -48,7 +48,7 @@ Contract Code:
  - Before: `my_func<S: Storage, A: Api>(deps: &Extern<S, A>, ...`
  - After: `my_func<S: Storage, A: Api, Q: Querier>(deps: &Extern<S, A, Q>, ...`
  - Remember to add `use cosmwasm_std::Querier;`
  -- `query` now returns `Result<Binary>` not `Result<Vec<u8>>`
  +- `query` now returns `StdResult<Binary>` instead of `Result<Vec<u8>>`
  - You can also replace `to_vec(...)` with `to_binary(...)`
  - No `.context(...)` is required after `from_slice` and `to_vec`, they return
  proper `cosmwasm_std::Error` variants on errors.
  