Fix Style/HashSlice cop violations (#33720)

app/lib/activitypub/adapter.rb

@@ -17,7 +17,7 @@ class ActivityPub::Adapter < ActiveModelSerializers::Adapter::Base
 
     options         = serialization_options(options)
     serialized_hash = serializer.serializable_hash(options.merge(named_contexts: named_contexts, context_extensions: context_extensions))
-    serialized_hash = serialized_hash.select { |k, _| options[:fields].include?(k) } if options[:fields]
+    serialized_hash = serialized_hash.slice(*options[:fields]) if options[:fields]
     serialized_hash = self.class.transform_key_casing!(serialized_hash, instance_options)
 
     { '@context': serialized_context(named_contexts, context_extensions) }.merge(serialized_hash)