2.5.0rc6: Bug fixes

What's Changed

• Add docs for Flower integration by @nvkevlu in #2862
• Update simulator folder path for random forest example by @ZiyueXu77 in #2865
• Fix an XGB Failure caused by len() by @nvidianz in #2863
• Fed Stats Notebooks and Read ME: fix fed stats output directory due to simulator output structure changes by @chesterxgchen in #2864
• Fixed the wrong dh_psi_task_handler path by @yhwen in #2866
• improve race condition handling by @yanchengnv in #2867
• support passing custom env vars for flower client by @yanchengnv in #2870
• Gradient inversion: fix cross-validation path by @holgerroth in #2869
• Update Job API docs after redesign by @SYangster in #2873
• Updated xgboost user guide by @nvidianz in #2872
• Add pipe docstring by @YuanTingHsieh in #2868
• Update flower examples by @YuanTingHsieh in #2871

Full Changelog: 2.5.0rc5...2.5.0rc6