Remove vestigial RBS definition of `Config#health_check`. #2278

Job	Run time
lint-workflows	13s
ci-check (run_each_gem_spec, 3.4, elasticsearch:9.0.0)	16m 24s
ci-check (run_specs_with_vcr, 3.4, elasticsearch:9.1.0)	10m 25s
ci-check (run_misc_checks, 3.4, elasticsearch:9.1.0)	12m 34s
ci-check (run_each_gem_spec, 3.4, opensearch:2.19.0)	17m 8s
docker-demo	2m 58s
ci-check (run_each_gem_spec, 3.4, elasticsearch:9.1.0)	17m 15s
ci-check (run_each_gem_spec, 3.4, opensearch:3.1.0)	17m 29s
ci-check (run_specs_file_by_file, 3.4, elasticsearch:9.1.0)	20m 16s
All CI Checks Passed	11s
	1h 54m 53s

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