Fixes following clang -Wdocumentation warning:
```
flatbuffers.h:1762:17: error: parameter ']' not found in the function declaration [-Werror,-Wdocumentation]
/// @param[in]] v A const reference to the `std::vector` of structs to
```
/// `vector`.
/// @tparam T The data type of the `std::vector` struct elements.
/// @tparam S The data type of the `std::vector` native struct elements.
- /// @param[in]] v A const reference to the `std::vector` of structs to
+ /// @param[in] v A const reference to the `std::vector` of structs to
/// serialize into the buffer as a `vector`.
/// @return Returns a typed `Offset` into the serialized data indicating
/// where the vector is stored.