Require Ruby 2.5 for Rails 6.

Generally followed the pattern for https://github.com/rails/rails/pull/32034

* Removes needless CI configs for 2.4
* Targets 2.5 in rubocop
* Updates existing CHANGELOG entries for fewer merge conflicts
* Removes Hash#slice extension as that's inlined on Ruby 2.5.
* Removes the need for send on define_method in MethodCallAssertions.

1 files changed, 0 insertions, 23 deletions

diff --git a/activesupport/lib/active_support/core_ext/hash/slice.rb b/activesupport/lib/active_support/core_ext/hash/slice.rb
index e07a5498ff..3d0f8a1e62 100644
--- a/activesupport/lib/active_support/core_ext/hash/slice.rb
+++ b/activesupport/lib/active_support/core_ext/hash/slice.rb
@@ -1,29 +1,6 @@
 # frozen_string_literal: true
 
 class Hash
-  # Slices a hash to include only the given keys. Returns a hash containing
-  # the given keys.
-  #
-  #   { a: 1, b: 2, c: 3, d: 4 }.slice(:a, :b)
-  #   # => {:a=>1, :b=>2}
-  #
-  # This is useful for limiting an options hash to valid keys before
-  # passing to a method:
-  #
-  #   def search(criteria = {})
-  #     criteria.assert_valid_keys(:mass, :velocity, :time)
-  #   end
-  #
-  #   search(options.slice(:mass, :velocity, :time))
-  #
-  # If you have an array of keys you want to limit to, you should splat them:
-  #
-  #   valid_keys = [:mass, :velocity, :time]
-  #   search(options.slice(*valid_keys))
-  def slice(*keys)
-    keys.each_with_object(Hash.new) { |k, hash| hash[k] = self[k] if has_key?(k) }
-  end unless method_defined?(:slice)
-
   # Replaces the hash with only the given keys.
   # Returns a hash containing the removed key/value pairs.
   #