fix: typo in React-cxxreact.podspec (#49879)

Summary:
This pull request includes a minor change to the `React-cxxreact.podspec` file in the `ReactCommon/cxxreact` package. The change corrects a typo in the `HEADER_SEARCH_PATHS` configuration.

## Changelog:

[IOS] [FIXED] - Corrected the path from `"$(PODS_ROOT)/fas_float/include"` to `"$(PODS_ROOT)/fast_float/include"` in the `HEADER_SEARCH_PATHS` configuration.

Pull Request resolved: https://github.com/facebook/react-native/pull/49879

Reviewed By: rshest

Differential Revision: D70773742

Pulled By: javache

fbshipit-source-id: 0823732bf45c8c17ee7d4c0c3542be5c286445ba