Administration: Use HTTPS for XHTML Friends Network URL.

Props raajtram, jrf, passoniate, bookdude13, sabernhardt, audrasjb.
Fixes #48002.
Built from https://develop.svn.wordpress.org/trunk@48292


git-svn-id: https://core.svn.wordpress.org/trunk@48061 1a063a9b-81f0-0310-95a4-ce76da25c4cd