Filesystem API: Use correct variable when closing the file handle in...

Filesystem API: Use correct variable when closing the file handle in `WP_Filesystem_FTPext::get_contents()`.

Props gothick@gothick.org.uk.
Merges [48797] to the 5.5 branch.
Fixes #51029.
Built from https://develop.svn.wordpress.org/branches/5.5@48803


git-svn-id: https://core.svn.wordpress.org/branches/5.5@48565 1a063a9b-81f0-0310-95a4-ce76da25c4cd