net/http: remove DualStack in DefaultTransport
Removing `DualStack` from `http.DefaultTransport` since it is deprecated
https://github.com/golang/go/blob/master/src/net/dial.go#L61
Change-Id: Id8ea1e68796ef8a8d49f7a04d0c4815aa92a1804
GitHub-Last-Rev:
0907b59fa793dafc764188c70487a61a720bbc7c
GitHub-Pull-Request: golang/go#41233
Reviewed-on: https://go-review.googlesource.com/c/go/+/253198
Reviewed-by: Damien Neil <dneil@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Trust: Damien Neil <dneil@google.com>
Trust: Brad Fitzpatrick <bradfitz@golang.org>