[ci][train] Remove unnecessary xgboost_ray/lightgbm_ray reinstalls for release tests

[justinvyu]

Why are these changes needed?

#42111 removed classes that were depended on by the latest release of xgboost_ray. The master branch of this external library has some changes that remove this dependency, which was updated in ml/core-requirements.txt.

However, post build scripts for release tests install the latest version of these libraries, causing all these release test failures. We should test with the master version of the external libraries. This is a temporary measure, since we are planning to remove xgboost_ray and lightgbm_ray dependencies from Ray for 2.10 (to finish within 2 weeks).

Related issue number

Closes #43155
Closes #43161
Closes #43163
Closes #43156
Closes #43157
Closes #43158
Closes #43159

Checks

• I've signed off every commit(by using the -s flag, i.e., git commit -s) in this PR.
• I've run scripts/format.sh to lint the changes in this PR.
• I've included any doc changes needed for https://docs.ray.io/en/master/.
  • I've added any new APIs to the API Reference. For example, if I added a
    method in Tune, I've added it in doc/source/tune/api/ under the
    corresponding .rst file.
• I've made sure the tests are passing. Note that there might be a few flaky tests, see the recent failures at https://flakey-tests.ray.io/
• Testing Strategy
  • Unit tests
  • Release tests
  • This PR is not tested :(

[justinvyu]

@aslonnie Addressed your comment. Could I get another review / approval? This is to fix broken release tests.

[aslonnie]

this also works.

I thought you wanted to update the deps in ml/core-requirements

[justinvyu]

ml/core-requirements is not included in these release tests for some reason. See my attempt here: https://buildkite.com/ray-project/release/builds/8456#018da94d-2df2-4022-a383-63293e561427

I'm not going to spend time to figure it out since I am trying to remove this dependency within a week.