Bump golang.org/x/net to HEAD for http2 go1.27 wrap fixes

Updates golang.org/x/net to v0.55.1-0.20260602153038-42abb857022c to pick up
the go1.27 http2 "wrap" fixes:

- CL 782940 (golang/go#79642): configureServer registers the h2 and http/1.1
  ALPN protocols on s.TLSConfig.
- CL 785900 (golang/go#79778): ConfigureTransport/ConfigureTransports enable
  HTTP/2 on the transport and keep TLSClientConfig non-nil.

With both, the kube-apiserver secure-serving path and the client-go / apiserver
HTTP/2 clients negotiate HTTP/2 under go1.27 with no Kubernetes-side changes;
no workaround is needed.

Gerrit: https://go-review.googlesource.com/c/net/+/782940
Gerrit: https://go-review.googlesource.com/c/net/+/785900
Signed-off-by: Davanum Srinivas <davanum@gmail.com>

Kubernetes-commit: 544a4612cd73250f69e6a95f4b3de8b94112e594