chore: remove custom transform_keys monkey-patch, bump to 0.4.7.persona

Ruby has included Hash#transform_keys natively since 2.5, so the custom
implementation is no longer needed. Ported from upstream PR bhgames#37.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: ErnestChiu2023

json_logic.gemspec

@@ -18,7 +18,7 @@ Gem::Specification.new do |spec|
   end
   spec.require_paths = ['lib']
 
-  spec.required_ruby_version = '>= 2.2'
+  spec.required_ruby_version = '>= 2.5'
 
   spec.add_development_dependency 'bundler',  '>= 2.0.1'
   spec.add_development_dependency 'rake',     '>= 10.0'

lib/core_ext/stringify_keys.rb

@@ -1,20 +1,4 @@
 class Hash
-  # Stolen from ActiveSupport
-  def transform_keys
-    return enum_for(:transform_keys) { size } unless block_given?
-    result = {}
-    each_key do |key|
-      result[yield(key)] = self[key]
-    end
-    result
-  end
-
-  # Returns a new hash with all keys converted to strings.
-  #
-  #   hash = { name: 'Rob', age: '28' }
-  #
-  #   hash.stringify_keys
-  #   # => {"name"=>"Rob", "age"=>"28"}
   def stringify_keys
     transform_keys(&:to_s)
   end

lib/json_logic/version.rb

@@ -1,3 +1,3 @@
 module JSONLogic
-  VERSION = '0.4.6.persona'
+  VERSION = '0.4.7.persona'
 end