docs: Add sbomified badge #4909

Job	Run time
functional_tests (stable)	2m 51s
unit_tests (stable)	3m 11s
functional_tests (beta)	2m 51s
end2end_test_prep	1m 20s
unit_tests (beta)	3m 18s
end2end_test_staging	3m 11s
end2end_test_12	2m 6s
end2end_test_34	2m 1s
end2end_test_56	1m 59s
sbom_provenance	0s
push_prod_virtualenv_image	0s
push_canary_virtualenv_image	0s
push_prod_secondary_image	0s
push_canary_secondary_image	0s
provenance_prod_virtualenv_image	0s
provenance_prod_secondary_image	0s
provenance_canary_virtualenv_image	0s
provenance_canary_secondary_image	0s
push_staging_virtual_env_images	0s
push_staging_secondary_image	0s
push_staging_observable_secondary_image	0s
	22m 48s

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