Remove duplicate cors header for download network endpoint #3854

Job	Run time
coverage	18m 44s
matrix	17s
build / linux-amd64-pinned-all	1h 23m 45s
build / macos-amd64-pinned-all	1h 26m 50s
build / windows-amd64-pinned-unittest	39m 0s
build / windows-amd64-pinned-contract	21m 12s
build / windows-amd64-pinned-integration	1h 30m 8s
build / windows-amd64-pinned-tools	23m 7s
build / status	1s
	6h 3m 4s

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