Bug 1598042 [wpt PR 20334] - [Azure Pipelines] drop references to 'Hosted Windows Client Next', a=testonly

Automatic update from web-platform-tests
[Azure Pipelines] drop references to 'Hosted Windows Client Next' (#20334)

We don't use this anymore.
--

wpt-commits: 41c8e340efa48f39526da219d4fedebe1ec5ff1f
wpt-pr: 20334

testing/web-platform/tests/.azure-pipelines.yml

@@ -11,9 +11,7 @@
 # project is required:
 #  - The "Build pull requests from forks of this repository" setting must be
 #    enabled: https://docs.microsoft.com/en-us/azure/devops/pipelines/repos/github#validate-contributions-from-forks
-#  - Self-hosted agents for Windows 10 are used:
-#    - 'Hosted Windows Client' is the latest Windows 10
-#    - 'Hosted Windows Client Next' is Windows 10 Insider Preview
+#  - A self-hosted Windows 10 agent pool named 'Hosted Windows Client'.
 #    Documention for the setup of these agents:
 #    https://docs.microsoft.com/en-us/azure/devops/pipelines/agents/v2-windows