Bump mem and react-native in /examples

Removes [mem](https://github.com/sindresorhus/mem). It's no longer used after updating ancestor dependency [react-native](https://github.com/facebook/react-native). These dependencies need to be updated together.


Removes `mem`

Updates `react-native` from 0.60.0 to 0.70.6
- [Release notes](https://github.com/facebook/react-native/releases)
- [Changelog](https://github.com/facebook/react-native/blob/main/CHANGELOG.md)
- [Commits](facebook/react-native@v0.60.0...v0.70.6)

---
updated-dependencies:
- dependency-name: mem
  dependency-type: indirect
- dependency-name: react-native
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>