net/http: incorrect self link in package documentation

[perillo]

What version of Go are you using (go version)?

$ go version
go version go1.17.6 linux/amd64

Does this issue reproduce with the latest release?

Yes, including tip.

Description

The link https://golang.org/pkg/net/http/#example_ResponseWriter_trailers is incorrect, since the html ID of the example is example-ResponseWriter-Trailers.

[cherrymui]

That link is at https://cs.opensource.google/go/go/+/master:src/net/http/h2_bundle.go;l=6269 , which in turn is from x/net/http2/server.go https://cs.opensource.google/go/x/net/+/master:http2/server.go;l=2550

cc @neild

[seankhliao]

related #48707