net/http: strip request body headers on POST to GET redirects
According to WHATWG Fetch, when the body is dropped in a redirect,
headers that describe the body should also be dropped.
https://fetch.spec.whatwg.org/#http-redirect-fetch
Fixes #57273
Change-Id: I84598f69608e95c1b556ea0ce5953ed43bf2d824
Reviewed-on: https://go-review.googlesource.com/c/go/+/710395
Auto-Submit: Damien Neil <dneil@google.com> Reviewed-by: Michael Pratt <mpratt@google.com> Reviewed-by: Damien Neil <dneil@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>