fix: Add nkf and base64 to Gemfile for Ruby 3.4 compatibility (#55346)

Summary:
Ruby 3.4 removed 'kconv' (which requires 'nkf') and 'base64' from the standard library. This commit adds them to the Gemfiles to fix 'pod install' failures on Ruby 3.4 environments.

## Changelog:
[iOS][Fixed] - Add `nkf` and `base64` as ruby dependencies

Pull Request resolved: #55346

Reviewed By: cortinico

Differential Revision: D92147798

Pulled By: cipolleschi

fbshipit-source-id: ac06369593df2b892d343f45d3c43795c079a461

Author: kimchi-developer

packages/rn-tester/Gemfile

@@ -16,3 +16,6 @@ gem 'bigdecimal'
 gem 'logger'
 gem 'benchmark'
 gem 'mutex_m'
+gem 'nkf'
+gem 'base64'
+

private/helloworld/Gemfile

@@ -12,5 +12,8 @@ gem 'bigdecimal'
 gem 'logger'
 gem 'benchmark'
 gem 'mutex_m'
+gem 'nkf'
+gem 'base64'
+
 gem 'ffi',  '>= 1.17.2'
 gem 'rexml', '>= 3.3.9'