test(button): add ionic mode to outline (#29702)

core/src/components/button/test/outline/button.e2e.ts

@@ -1,8 +1,7 @@
 import { expect } from '@playwright/test';
 import { configs, test } from '@utils/test/playwright';
 
-// TODO(ROU-5474): add tests for ionic theme
-configs().forEach(({ title, screenshot, config }) => {
+configs({ modes: ['ios', 'md', 'ionic-md'] }).forEach(({ title, screenshot, config }) => {
   test.describe(title('button: outline'), () => {
     test('should not have visual regressions', async ({ page }) => {
       await page.goto(`/src/components/button/test/outline`, config);