* [CI] Improve JVM test in GitHub Actions
* Use env var for Wagon options [skip ci]
* Move the retry flag to pom.xml [skip ci]
* Export env var RABIT_MOCK to run Spark tests [skip ci]
* Correct location of env var
* Re-try up to 5 times [skip ci]
* Don't run distributed training test on Windows
* Fix typo
* Update main.yml
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