Site Health: Modify the grading indicator to remove percentage score in favor of a "Good" or "Should be improved" status.
This removes arbitrary confusion about what the numbers mean.
Props Clorith, hedgefield, Cybr, arena, DavidAnderson, earnjam, daveshine, Otto42, azaozz, asadkn, KARTHOST, tigertech, maximejobin, johnbillion, raboodesign, ramiy, afragen.
Fixes #47046.
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