[Bug]: sp-picker-button quiet styles need to be updated

[Rocss]

Code of conduct

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Impacted component(s)

sp-picker-button

Expected behavior

spectrum-PickerButton--low was removed, according to: https://opensource.adobe.com/spectrum-css/pickerbutton.html#migrationguide
Therefore, we should update this component's CSS to process spectrum-PickerButton--quiet instead of spectrum-PickerButton--low for quiet style.

Actual behavior

Observe in the documentation how the quiet style is identical to the default one:

Screenshots

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What browsers are you seeing the problem in?

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How can we reproduce this issue?

1. Go to https://opensource.adobe.com/spectrum-web-components/components/picker-button/#quiet
2. Observe that the quiet styles are no longer applied

Sample code that illustrates the problem

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Logs taken while reproducing problem

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