[CI] Use Ubuntu 18.04 LTS in JVM CI, because 19.04 is EOL#5537

Merged

hcho3 merged 1 commit intodmlc:masterfrom hcho3:use_lts_in_ci

Apr 15, 2020

+1-1

Commits on Apr 15, 2020

[CI] Use Ubuntu 18.04 LTS in JVM CI, because 19.10 is EOL
hcho3
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