chore: set workers explicitly in playwright (#2641)

Author: kettanaito

test/browser/playwright.config.ts

@@ -9,6 +9,7 @@ export default {
   ],
   timeout: 10_000,
   retries: process.env.CI ? 1 : undefined,
+  workers: process.env.CI ? 3 : undefined,
   use: {
     trace: 'on-first-retry',
     launchOptions: {