SimplePie: Merge 5e046a3 from upstream. props rlerdorf, see #24210.

https://github.com/simplepie/simplepie/commit/5e046a3e681f82b1294c4418d8c773e9cf7c9fa0



git-svn-id: https://core.svn.wordpress.org/trunk@24589 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Use correct variable when calling request_filesystem_credentials() in delete_theme(). see #24210.



git-svn-id: https://core.svn.wordpress.org/trunk@24590 1a063a9b-81f0-0310-95a4-ce76da25c4cd