CustomGradientPicker: Prepare `Button`s for 40px default size #108916

Job	Run time
Compute current and next stable release branches	0s
Bump version	0s
Build Release Artifact	5m 12s
Create Release Draft and Attach Asset	0s
Revert version bump if build failed	0s
Publish WordPress packages to npm	0s
	5m 12s

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