Updated `$_old_files` to include SimplePie Core file #29336

Job	Run time
Determine Matrix	4s
Multisite Memcached / Test before	12m 55s
Single Site Default / Test before	13m 34s
Single Site Memcached / Test before	13m 12s
Multisite Memcached / Test current	13m 9s
Multisite Default / Test current	13m 5s
Single Site Default / Test current	12m 45s
Single Site Memcached / Test current	12m 22s
Multisite Default / Test before	17m 30s
Slack Notifications	0s
Compare / Single Site Memcached	19s
Compare / Multisite Default	11s
Compare / Single Site Default	10s
Compare / Multisite Memcached	15s
Failed workflow tasks	0s
	1h 49m 31s

Provide feedback