net/http: update bundled x/net/http2
Updates bundled http2 to x/net git rev
ef20fe5d7 for:
http2: make Transport.IdleConnTimeout consider wall (not monotonic) time
https://golang.org/cl/208798 (#29308)
http2: make CipherSuites validation error more verbose
https://golang.org/cl/200317 (#34776)
http2: track unread bytes when the pipe is broken
https://golang.org/cl/187377 (#28634)
http2: split cookie pair into separate hpack header fields
https://golang.org/cl/155657 (#29386)
Fixes #29308
Fixes #28634
Change-Id: I71a03ca62ccb5ff35a5cfadd8dc705a4491ae7ea
Reviewed-on: https://go-review.googlesource.com/c/go/+/209077
Reviewed-by: Ian Lance Taylor <iant@golang.org>