ci: Remove migrated libraries from downstream protobuf check #17293

Job	Run time
gitignore_correctness	1m 6s
owlbot-yaml	1m 10s
generate-readme	1m 12s
gapic-bom	1m 38s
root-pom	1m 40s
package_name_check	1m 7s
group_id_check_for_maps_libraries	8m 10s
owlbot-py	1m 16s
	17m 19s

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