Remove create_singletons()

Remove a small piece of code revealed by #5647 (comment 2436167278).

It originally helped with static initialisation order, but isn't needed since b9517430, and now only forces certain statics to be loaded immediately instead of lazily.

mentioned in issue #5647

requested review from @doctormo

approved this merge request

added this merge request to the merge train at position 2

merged