(testing/playwright) clarify how to set testing token env var (#2027)

docs/testing/playwright/overview.mdx

@@ -58,7 +58,7 @@ description: Use Playwright to write end-to-end tests with Clerk.
   ```
 
   > [!NOTE]
-  > You can manually set the Testing Token by using the `CLERK_TESTING_TOKEN` environment variable instead of calling `clerkSetup()`.
+  > Instead of calling `clerkSetup()`, you can manually set the Testing Token by setting the `CLERK_TESTING_TOKEN` environment variable to the [Testing Token](/docs/testing/overview#testing-tokens) that you create through the Backend API.
 
   ## Use `setupClerkTestingToken()`