Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/43920
React native is shipped as a whole, so it makes no sense for individual pods to specify which version of boost they support.
With this change we let the `react_native_pods` and the `boost.podspec` file to decide which version of boost is supported and all the other podspecs will follow.
## Changelog:
[Internal] - Remove explicit boost version from other podspecs
Reviewed By: NickGerleman
Differential Revision: D55801708
fbshipit-source-id: 3dcbbfb25010d2ee615afc4acfd5232fdc0c2a14