Bump up ubuntu version #2017

Job	Run time
build (2_12, mima)	1m 3s
build (2_12, e2e)	5s
conformance	1m 40s
build (2_12, test)	9m 52s
build (2_13, mima)	1m 8s
build (2_13, e2e)	5s
build (2_13, test)	8m 39s
build (3, mima)	6s
build (3, e2e)	4s
build (3, test)	8m 47s
build (2_12, examples_and_formatting)	2m 29s
build (2_13, scala3_compat_test)	7m 58s
build (3, scala3_compat_test)	9m 22s
ci-passed	3s
	51m 21s

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