Enable json_limited_encoder ff by default

This feature flag has been enabled globally for a while

Let's enable it by default as a step to finally removing it

Changelog: added

config/feature_flags/development/json_limited_encoder.yml

@@ -5,4 +5,4 @@ rollout_issue_url:
 milestone: '13.3'
 type: development
 group: group::source code
-default_enabled: false
+default_enabled: true

lib/gitlab/json.rb

@@ -248,7 +248,7 @@ 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)
+        return ::Gitlab::Json.dump(object) unless Feature.enabled?(:json_limited_encoder, default_enabled: :yaml)
 
         buffer = StringIO.new
         buffer_size = 0