Description

Fixes wordpress-mobile/gutenberg-mobile#3800 by updating the styling of the UnitControl unit button to look like a normal label when there is only a single unit option available (for example, "Pixel"). When this is the case the unit button is disabled and treated just as label and should only look like a label.

How has this been tested?

The easiest way to test is to either figure out a block that has a setting that uses UnitControl but only has a single unit to pick from, or to change the isPickerButtonEnabled const to return false like this:

const isPickerButtonEnabled = false;

1. Then add that block to the editor, click on the settings cog, and verify the color of the unit option in the UnitControl. The screenshots below are from the Column block for example.
2. Also test that a block setting with multiple units available acts as a button that when tapped, opens the options to select a different unit (if you made changes to isPickerButtonEnabled, be sure to revert that change first).

Screenshots

Before	After

Types of changes

Small styling changes that should not break anything.

Checklist:

• My code is tested.
• My code follows the WordPress code style.
• My code follows the accessibility standards.
• I've tested my changes with keyboard and screen readers.
• My code has proper inline documentation.
• I've included developer documentation if appropriate.
• I've updated all React Native files affected by any refactorings/renamings in this PR (please manually search all *.native.js files for terms that need renaming or removal).