Support public_name in json for speaker

Cf. https://github.com/pretalx/pretalx/issues/1910

app/jobs/pretalx/import_job.rb

@@ -38,7 +38,7 @@ module Pretalx
               session.url = session_data['url']
               session.speakers = session_data['persons'].map do |speaker_data|
                 Speaker.find_or_initialize_by(ref_id: speaker_data['guid'], conference:).tap do |speaker|
-                  speaker.name = speaker_data['name']
+                  speaker.name = speaker_data['name'] || speaker_data['public_name']
                   speaker.description = simple_format(speaker_data['biography'])
                   speaker.save!
                 end