Fixed `POST` and `DELETE /_dangling/{index_uuid}` returning `202` #1631

Job	Run time
test-opensearch-spec (version=1.3.17, hub=opensearchproject, tests=default)	1m 25s
test-opensearch-spec (version=2.0.0, hub=opensearchproject, tests=default)	1m 19s
test-opensearch-spec (version=2.18.0, hub=opensearchproject, tests=default)	1m 45s
test-opensearch-spec (version=2.18.0, hub=opensearchproject, tests=plugins/index_state_management)	1m 3s
test-opensearch-spec (version=2.18.0, hub=opensearchproject, tests=plugins/ml)	2m 14s
test-opensearch-spec (version=2.18.0, hub=opensearchproject, tests=routing)	1m 19s
test-opensearch-spec (version=2.18.0, hub=opensearchproject, tests=snapshot)	1m 2s
test-opensearch-spec (version=2.18.0, hub=opensearchproject, tests=dangling)	59s
test-opensearch-spec (version=2.18.0, hub=opensearchproject, tests=plugins/replication)	1m 6s
test-opensearch-spec (version=2.18.0, hub=opensearchproject, tests=plugins/streaming)	1m 30s
test-opensearch-spec (version=2.18.0, hub=opensearchproject, tests=plugins/notifications)	54s
test-opensearch-spec (version=2.18.0, hub=opensearchproject, tests=plugins/query_insights)	1m 9s
test-opensearch-spec (version=2.18.0, hub=opensearchproject, tests=plugins/workload-management)	1m 10s
test-opensearch-spec (version=2.18.0, hub=opensearchproject, tests=plugins/analysis)	1m 18s
test-opensearch-spec (version=2.19.0, hub=opensearchstaging, tests=default)	1m 49s
test-opensearch-spec (version=3.0.0, hub=opensearchstaging, tests=default)	1m 57s
merge-coverage	6s
	22m 5s

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