tests(smoke): attempt to fix cls-elements flake

[paulirish]

@connorjclark reported a flake about layout-shift-elements..

the test page actually has 1 shifted element.. however in #10877 @patrickhulce tweaked the page to try add so many dom nodes that the originally shifted element is no longer identifiable.. presumably evicted from the backend node cache.

the flake result that connor got suggested the node was still found on his machine. So my attempted fix is just to create MOAR NODES. 🤷

i've personally never seen this flake on my two machines, so @connorjclark you'll have to try this out.

ref the smoke flakes issue #11341

[connorjclark]

This URL change doesn't seem necessary, or better?

[paulirish]

the test is all about DOM elements that are no longer in the DOM ("removed") and also that are not available to the protocol due to being evicted from some DOM node cache.

even if all this test was looking at was the first part, i'd still be lobbying for a rename from "missing" to "removed" as that's the more typical term.
but since this situation is more about REMOVED+EVICTED (which is why we're doing the rerenders) i'd like to be using the most clear term.

you can also see where i edited Patrick's PR description for more context.
#10877

(background: i was trying to understand the point of this test. i saw "missing" and concluded it was all about DOM elements just being removed from the DOM. that led to a buncha confusion)