refactored `modal-provider.js` imports to use `lib` instead of `web`. Also removed `modal-provider.js` in `web` since it is no longer being called
Next Steps:
# Refacor `modal.react.js` in `landing`
# Refactor `modal-provider.js` imports in `landing` to use `lib` instead of `landing`
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Depends on D5354
Linear Task: [[ https://linear.app/comm/issue/ENG-2038/refactor-modal-into-lib | ENG-2038 ]]