A legacy K8s test fails due to incorrect usage of @ray.method which only started raising errors after the Ray 1.12.0 branch cut.
This PR removes the use of @ray.method in the test.
Some context in #23271 and #23471
In addition, I noticed some of the test were flakey due to out-of-memory issues. For that reason, I've doubled the memory request and limits in the legacy operator's example files.
I've also added CPU limits in an example file that was missing them -- it makes the most sense for consistency with Ray's resource model to use CPU limits in K8s configs.
Finally, I added an extra note to the instructions for running the tests.
