net/http: document streaming nature of Response.Body
net/http: document streaming nature of Response.Body

Fixes #22873

Change-Id: Ib2b7ee42a23b84db21cdfa693b62d5e6fbfdb54e
Reviewed-on: https://go-review.googlesource.com/80075
Reviewed-by: Tom Bergan <3b77d7da34779f829901a664ac7c87d255b041af@google.com>

Cofyc/go,CAFxX/go,nawawi/go,nawawi/go,codestation/go,josharian/go,akutz/go,nawawi/go,cloudflare/go,akutz/go,codestation/go,golang/go,codestation/go,nawawi/go,christopher-henderson/Go,josharian/go,josharian/go,nawawi/go,josharian/go,nawawi/go,codestation/go,josharian/go,golang/go,CAFxX/go,CAFxX/go,codestation/go,Cofyc/go,CAFxX/go,cloudflare/go,CAFxX/go,cloudflare/go,akutz/go,josharian/go,golang/go,cloudflare/go,codestation/go,golang/go,akutz/go,CAFxX/go,Cofyc/go,codestation/go,golang/go,codestation/go,cloudflare/go,golang/go,golang/go,akutz/go,CAFxX/go,akutz/go,CAFxX/go,cloudflare/go,nawawi/go,cloudflare/go,josharian/go,cloudflare/go,akutz/go,Cofyc/go,Cofyc/go,akutz/go,golang/go,josharian/go,Cofyc/go,Cofyc/go,Cofyc/go,nawawi/go