net/http: server responds with Transfer-Encoding: identity [1.17 backport]

[gopherbot]

@neild requested issue #49194 to be considered for backport to the next 1.17 minor release.

@gopherbot Please open backport issues for 1.16 and 1.17

[gopherbot]

Change https://golang.org/cl/368087 mentions this issue: [release-branch.go1.17] net/http: do not send Transfer-Encoding: identity in responses

[gopherbot]

Closed by merging 3c50f27 to release-branch.go1.17.