Optimize map { ... }.compact calls (#15513)

* Optimize map { ... }.compact

using Enumerable#filter_map, supported since Ruby 2.7

* Add poyfill for Enumerable#filter_map

app/services/activitypub/process_poll_service.rb

@@ -30,7 +30,7 @@ class ActivityPub::ProcessPollService < BaseService
 
     voters_count = @json['votersCount']
 
-    latest_options = items.map { |item| item['name'].presence || item['content'] }.compact
+    latest_options = items.filter_map { |item| item['name'].presence || item['content'] }
 
     # If for some reasons the options were changed, it invalidates all previous
     # votes, so we need to remove them