message: Remove outdated return code comments
diff: @@ -75,7 +75,6 @@ where
  }),
  // Writes the given value into the database entry at the given key.
  // Ownership of both input and output pointer is not transferred to the host.
  - // Returns 0 on success. Returns negative value on error.
  "db_write" => Func::new(move |ctx: &mut Ctx, key_ptr: u32, value_ptr: u32| -> VmResult<()> {
  do_write::<S, Q>(ctx, key_ptr, value_ptr)
  }),
  @@ -83,7 +82,6 @@ where
  // scans will not find this key.
  // At the moment it is not possible to differentiate between a key that existed before and one that did not exist (https://github.com/CosmWasm/cosmwasm/issues/290).
  // Ownership of both key pointer is not transferred to the host.
  - // Returns 0 on success. Returns negative value on error.
  "db_remove" => Func::new(move |ctx: &mut Ctx, key_ptr: u32| -> VmResult<()> {
  do_remove::<S, Q>(ctx, key_ptr)
  }),
  