[enrollment] Reenable device attribute prompt test

Reenable TestAttributePromptPageGetsLoaded test on ChromeOS.

Bug: chromium:1454755
Test browser_tests --gtest_filter="EnterpriseEnrollmentTest.TestAttributePromptPageGetsLoaded"

Change-Id: I35e3b62f063b73f598ad9e19c53c0077f6bf2116
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5433081


Commit-Queue: Artem Sumaneev <asumaneev@google.com>
Reviewed-by: Danila Kuzmin <dkuzmin@google.com>
Cr-Commit-Position: refs/heads/main@{#1283845}