[xgboost][hotfix] fix readthedocs

[richardliaw]

Why are these changes needed?

For some reason, xgboost causes readthedocs to fail building. Seems related to readthedocs/readthedocs.org#4686

@krfricke

Related issue number

Checks

• 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 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 :(

[hcho3]

@ericl @richardliaw Hello, XGBoost dev here. The Python wheel for XGBoost 1.3.0 had a critical bug that rendered it unusable on CentOS and Debian platforms. I submitted dmlc/xgboost#6482 to fix the bug. Once dmlc/xgboost#6482 is approved and merged, we will release 1.3.0.post0 version to PyPI.

[hcho3]

The 1.3.0.post0 version is now available on PyPI: https://pypi.org/project/xgboost/1.3.0.post0/#files

[richardliaw]

Hey @hcho3 thanks a bunch for the heads up!