stage-cypress-tests: Use cypress-cloud instead of cy2 for running tests

cypress recently put effort on blocking sorry-cypress to avoid the use of the tool (see that swh-web build log).

sorry-cypress enables to run self-hosted tests in parallel without any cost and we use it in our CI.

So the sorry-cypress team develop a new tool called cypress-cloud enabling to bypass the cypress restrictions so the sorry-cypress tool can still be used.

So use the tool in our pipeline for swh-web.

Related to swh/devel/swh-web!1142 (db4cc0bb)