Increase required contrast for color suggestions
Increase required contrast for color suggestions

This CL increases the required contrast for the color suggestion
feature in the color picker to make sure that the new color is a truly
different CSS color.

Fixed: chromium:1166128
Change-Id: I24b4eb3988a0368d9f03cfa905265126a748af79
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/2637694
Reviewed-by: Mathias Bynens <17a2cbc4e33156874a9862b0f530521117e66a3d@chromium.org>
Commit-Queue: Alex Rudenko <d8d88e7d7e77f69e23d1d1432231196fb8e02a62@chromium.org>

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