chore: fix ios build for FabricExample

[satya164]

Description

I wasn't able to build and run the app locally as bundle install fails with the following error:

An error occurred while installing ffi (1.16.3),
and Bundler cannot continue.

In Gemfile:
  cocoapods was resolved to 1.15.2, which depends on
cocoapods-core was resolved to 1.15.2, which depends
on
      typhoeus was resolved to 1.4.1, which depends on
        ethon was resolved to 0.16.0, which depends on
          ffi

This fixes the build errors.

Changes

I updated the ffi version in Gemfile.lock to the version that works.

Also moved .ruby-version to the root of the app (same location as Gemfile) so rbenv can pick it up and use the correct Ruby version.

Test plan

Verified the changes by running the following commands on a fresh repo:

yarn
cd FabricExample
rbenv exec bundle install
rbenv exec bundle exec pod install --project-directory=ios
yarn ios

The Podfile.lock also got updated after the changes.

Checklist

• Included code example that can be used to test this change.
• For visual changes, included screenshots / GIFs / recordings documenting the change.
• For API changes, updated relevant public types.
• Ensured that CI passes