Update flipper in RNTester and template (facebook#31010)

Summary:
allow-large-files

RN Tester is using an old version of Flipper. This will help testing regressions in the latest version (which is installed when starting a new project). This also fixes an issue where libevent is incompatible between the one in flipper and when using hermes on iOS. To fix it I changed to use the version published on cocoapods instead of using a local podspec (see facebook/flipper#1916).

## Changelog

[General] [Changed] - Update flipper

Pull Request resolved: facebook#31010

Test Plan:
- Tested that RN tester builds and flipper works with hermes enabled / disabled and fabric on iOS
- Tested that RN tester builds and flipper works on Android

Reviewed By: fkgozali

Differential Revision: D26592317

Pulled By: PeteTheHeat

fbshipit-source-id: 2cd278c7a51b1859dab0465846b061221f07d3f6

(cherry picked from commit 3399896)