Documentation for 'no-async-tests' is misleading

[swinejelly]

The documentation for 'no async tests', while I agree the rule itself is extremely important to avoid this issue, seems to be misstating what Cypress will do.

The existing documentation implies that the example, incorrect test cases will error and fail, while what will really happen is those test cases will succeed even if the Cypress assertions in them fail, which makes this lint rule extremely important (the former would force people to fix their test cases, the latter will lead to test cases succeeding even when they should be failing).

I suggest until cypress-io/cypress#4742 can be fixed that we update these docs to describe the actual behavior which will emphasize the importance of this rule.

If someone can confirm my understanding I may be able to make a PR for this change myself.