[native] Upgrade to react-native@0.70.15

Summary: Was investigating if this introduce support in Hermes for named capture groups to address some issues integrating Viem in ENG-5308. It didn't end up helping, but I figured I'd put the diff up anyways.

Test Plan: Before landing, will confirm it passes CI, and that iOS / Android builds on dev / release

Reviewers: varun, will

Reviewed By: will

Subscribers: tomek

Differential Revision: https://phab.comm.dev/D13700