fix(`_streaming_download`): handle retry-level JSON error responses #2004

Job	Run time
client (test-functional, bookworm)	5m 32s
client (test-integration, bookworm)	1m 41s
client (test-random, bookworm)	2m 9s
component (export, bookworm)	2m 13s
component (keyring, bookworm)	56s
component (log, bookworm)	49s
component (proxy, bookworm)	2m 7s
internationalization (bookworm)	1m 38s
	17m 5s

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