ci: dependency check with BUILD_SUBDIR=java-spanner-jdbc #18127

Job	Run time
generate-readme	1m 27s
package_name_check	1m 2s
owlbot-py	1m 9s
root-pom	2m 0s
gapic-bom	1m 39s
owlbot-yaml	1m 1s
gitignore_correctness	1m 2s
group_id_check_for_maps_libraries	8m 21s
	17m 41s

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