chore: Remove the deprecated github check. #15550

Job	Run time
root-pom	1m 27s
gapic-bom	1m 28s
gitignore_correctness	48s
owlbot-py	56s
owlbot-yaml	49s
generate-readme	53s
package_name_check	48s
group_id_check_for_maps_libraries	6m 44s
	13m 53s

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