tests: limit LCP element audit to m87 and earlier

[patrickhulce]

Summary
LCP in Canary has flipped to including removed elements by default.

https://chromium-review.googlesource.com/c/chromium/src/+/2480845

Long-term we should find a way to surface this element and/or potentially keep 6.x on the old LCP version, but for now we'll make PRs landable again.

[brendankenny]

Long-term we should find a way to surface this element and/or potentially keep 6.x on the old LCP version

@patrickhulce do you mind filing a bug on this and maybe also mention removing this _maxChromiumMilestone entry in the issue?

One benefit of _minChromiumMilestone is that it eventually ages in and always runs since chrome versions only increase :) While _maxChromiumMilestone could easily slip by and appear to be functioning as a test when it isn't being checked against anything anymore, so we have to be slightly more vigilant (though ideally there'll be a new smoke test for the new behavior, so it won't really matter if there's also an old test hanging around not doing anything).

[patrickhulce]

done 👍

[brendankenny]

haha, I meant just this particular _maxChromiumMilestone entry, not support altogether :) Maybe we could come up with some expiration mechanism for it or something, but it does seem like there's not a good way to do this without a max companion to the min.

[connorjclark]

_failAt: new Date('2021-01-01') seems cool to me. ticking time bomb