Remove FF ci_new_artifact_file_reader

It was already enabled by default

config/feature_flags/development/ci_new_artifact_file_reader.yml

----
-name: ci_new_artifact_file_reader
-introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/40268
-rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/249588
-group: group::pipeline authoring
-type: development
-default_enabled: true

lib/gitlab/ci/artifact_file_reader.rb

@@ -45,14 +45,6 @@ module Gitlab
       end
 
       def read_zip_file!(file_path)
-        if ::Gitlab::Ci::Features.new_artifact_file_reader_enabled?(job.project)
-          read_with_new_artifact_file_reader(file_path)
-        else
-          read_with_legacy_artifact_file_reader(file_path)
-        end
-      end
-
-      def read_with_new_artifact_file_reader(file_path)
         job.artifacts_file.use_open_file do |file|
           zip_file = Zip::File.new(file, false, true)
           entry = zip_file.find_entry(file_path)
@@ -69,25 +61,6 @@ module Gitlab
         end
       end
 
-      def read_with_legacy_artifact_file_reader(file_path)
-        job.artifacts_file.use_file do |archive_path|
-          Zip::File.open(archive_path) do |zip_file|
-            entry = zip_file.find_entry(file_path)
-            unless entry
-              raise Error, "Path `#{file_path}` does not exist inside the `#{job.name}` artifacts archive!"
-            end
-
-            if entry.name_is_directory?
-              raise Error, "Path `#{file_path}` was expected to be a file but it was a directory!"
-            end
-
-            zip_file.get_input_stream(entry) do |is|
-              is.read
-            end
-          end
-        end
-      end
-
       def max_archive_size_in_mb
         ActiveSupport::NumberHelper.number_to_human_size(MAX_ARCHIVE_SIZE)
       end

lib/gitlab/ci/features.rb

@@ -63,10 +63,6 @@ module Gitlab
         ::Feature.enabled?(:ci_trace_log_invalid_chunks, project, type: :ops, default_enabled: false)
       end
 
-      def self.new_artifact_file_reader_enabled?(project)
-        ::Feature.enabled?(:ci_new_artifact_file_reader, project, default_enabled: true)
-      end
-
       def self.one_dimensional_matrix_enabled?
         ::Feature.enabled?(:one_dimensional_matrix, default_enabled: true)
       end

spec/lib/gitlab/ci/artifact_file_reader_spec.rb

@@ -18,17 +18,6 @@ RSpec.describe Gitlab::Ci::ArtifactFileReader do
         expect(YAML.safe_load(subject).keys).to contain_exactly('rspec', 'time', 'custom')
       end
 
-      context 'when FF ci_new_artifact_file_reader is disabled' do
-        before do
-          stub_feature_flags(ci_new_artifact_file_reader: false)
-        end
-
-        it 'returns the content at the path' do
-          is_expected.to be_present
-          expect(YAML.safe_load(subject).keys).to contain_exactly('rspec', 'time', 'custom')
-        end
-      end
-
       context 'when path does not exist' do
         let(:path) { 'file/does/not/exist.txt' }
         let(:expected_error) do