[6.x] Kill sibling transitions

[JayGeorge]

Description of the Problem

It seems like a few people don't like the loading transitions (#13637).

The idea initially was to trickle in entries very very very quickly (like… 0.01s) so that it didn't just feel like a stack of bricks falling on the page when data loaded in.

• While I still think this works well for smaller pages, I can see it getting annoying when you have 50+ entries on each page.
• The effect also feels more pronounced on larger monitors.

What this PR Does

• Removes sibling transitions but keeps the initial 0.125s transition.
• Hopefully this is a good halfway house, so the data still loads in like a feather pillow (but not 50 of them)

How to Reproduce

1. Navigate the CP and observe how it feels when data loads in