[Plugin: WordPress Popular Posts] Cron job 'wpp_my_hourly_event'

It probably is an old cronjob created by the very firsts versions of the plugin, a long while back. The latest versions of the plugin creates a cronjob called wpp_cache_event, which is deleted upon plugin deactivation.

You might want to try deleting it with this:

wp_clear_scheduled_hook('wpp_my_hourly_event');