Summary:
1. [ios] upgrade folly to 2021.06.28.00 which aligned to android.
2. folly compile setting from c++14 -> c++17: _this folly requires c++17 for `std::unordered_map::insert_or_assign`._
3. boost 1.63.0 -> 1.76.0: _the old boost does not support c++17._
4. deprecating react-native-community/boost-for-react-native: _by cocoapods installer, we could download the official target._
## Changelog
[iOS] [Changed] - Upgrade folly to 2021.06.28.00 and boost to 1.76.0
Pull Request resolved: https://github.com/facebook/react-native/pull/31840
Test Plan: CI passed
Reviewed By: fkgozali
Differential Revision: D29668480
Pulled By: yungsters
fbshipit-source-id: 98eae9ca47f489dcea91974e6f5e9dcb4d66c40c