avoid prominent and non-prominent in dropdown (microsoft#167244)

Author: sandy081

src/vs/workbench/contrib/extensions/browser/extensionsActions.ts

@@ -908,7 +908,7 @@ export class SkipUpdateAction extends AbstractUpdateAction {
 
 export class MigrateDeprecatedExtensionAction extends ExtensionAction {
 
-	private static readonly EnabledClass = `${ExtensionAction.LABEL_ACTION_CLASS} prominent migrate`;
+	private static readonly EnabledClass = `${ExtensionAction.LABEL_ACTION_CLASS} migrate`;
 	private static readonly DisabledClass = `${MigrateDeprecatedExtensionAction.EnabledClass} disabled`;
 
 	constructor(