refactor(ui5-color-palette-item): stableDomRef is obsolete (#3438)

The stableDomRef is meant for components that don't have a template on their own, but are pure elements, that the parent component renders (for example Select and Options). In this case the ColorPaletteItem is a component with own template and does not need to expose a special property like this to app developers to get its DOM ref as there is already getDomRef method that is sufficient.

BREAKING_CHANGE: stableDomRef is removed, if you need to get the item's DOM ref, use getDomRef on the item instance.

Author: ilhan007

packages/main/src/ColorPaletteItem.js

@@ -29,15 +29,6 @@ const metadata = {
 			type: CSSColor,
 		},
 
-		/**
-		 * Defines the stable selector that you can use via getStableDomRef method.
-		 * @type {String}
-		 * @public
-		 */
-		stableDomRef: {
-			type: String,
-		},
-
 		/**
 		 * Defines the tab-index of the element, helper information for the ItemNavigation.
 		 * @private