Enable JSON limited encoder

Changelog: performance

config/feature_flags/development/json_limited_encoder.yml

----
-name: json_limited_encoder
-introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/38687
-rollout_issue_url: 
-milestone: '13.3'
-type: development
-group: group::source code
-default_enabled: true

lib/gitlab/json.rb

@@ -248,8 +248,6 @@ module Gitlab
       # @return [String]
       # @raise [LimitExceeded] if the resulting json string is bigger than the specified limit
       def self.encode(object, limit: 25.megabytes)
-        return ::Gitlab::Json.dump(object) unless Feature.enabled?(:json_limited_encoder, default_enabled: :yaml)
-
         buffer = StringIO.new
         buffer_size = 0
 

spec/lib/gitlab/json_spec.rb

@@ -440,15 +440,5 @@ RSpec.describe Gitlab::Json do
         expect(subject.size).to eq(10001)
       end
     end
-
-    context 'when json_limited_encoder is disabled' do
-      let(:obj) { [{ test: true }] * 1000 }
-
-      it 'does not raise an error' do
-        stub_feature_flags(json_limited_encoder: false)
-
-        expect { subject }.not_to raise_error
-      end
-    end
   end
 end