chore(o11y): remove beta api from observability classes #17580

Job	Run time
generate-readme	1m 12s
owlbot-yaml	1m 4s
gitignore_correctness	1m 3s
group_id_check_for_maps_libraries	7m 56s
owlbot-py	1m 12s
gapic-bom	1m 44s
package_name_check	1m 14s
root-pom	1m 54s
	17m 19s

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