limit project expor retry to only 3

app/workers/project_export_worker.rb

 class ProjectExportWorker
   include Sidekiq::Worker
-  sidekiq_options queue: :gitlab_shell, retry: true
+  sidekiq_options queue: :gitlab_shell, retry: 3
   def perform(current_user_id, project_id)
     current_user = User.find(current_user_id)