Fix: Flaky CI test runs (#4770)

Because:
- We are seeing intermittent failures with `Ferrum::NoSuchTargetError`
being raised.

This commit:
- It appears to be an issue with the latest version of Ferrum,
configuring it with `flatten: false` is reported to fix it.

spec/support/cuprite.rb

@@ -15,6 +15,7 @@ def debug(*)
     app,
     window_size: [1200, 1200],
     browser_options: {},
+    flatten: false,
     process_timeout: 30,
     timeout: 60,
     inspector: true,