src/go.mod: sync golang.org/x/net with h2_bundle.go
CL 209077 updated bundled http2 to x/net git rev
ef20fe5d7 without
bumping the go.mod version.
Identified with the new go/packages based cmd/bundle from CL 189818.
$ go get golang.org/x/net@
ef20fe5d7
$ go mod tidy
$ go mod vendor
$ go generate -run bundle std # with CL 189818
Updates #32031
Change-Id: I581d35f33e2adafb588b2b0569648039187234a7
Reviewed-on: https://go-review.googlesource.com/c/go/+/209901
Run-TryBot: Filippo Valsorda <filippo@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>