4.5.1

• fix: cron in cluster mode was not restarting process after one pass - fixes #4834 #4733 #4307 #4834
• fix: restore --sort option on pm2 ls - fix #4536
• fix: fix tests with npm7
• fix: restore warning message about process list changed and not dumped
• chore: alias --cron with --cron-restart
• chore: test PM2 againt Node.js 15.x
• chore: upgrade systeminformation and debug module to latest - PR #4892 by @AdamMajer
• chore: drop Node 9.x from travis testing
• chore: remove ps-list module