net/http: 1.13rc1 docs for TimeoutHandler are incorrect about interfaces

[jmhodges]

As of Go 1.13rc1, net/http's TimeoutHandler does implement the Flusher interface that the docs of TimeoutHandler claims it does not. The fact that it does now implement Flusher is mentioned in the release docs for 1.13rc1, though.

TimeoutHandler also now implements Pusher which might be worth a mention in its docs.

[gopherbot]

Change https://golang.org/cl/191237 mentions this issue: net/http: change TimeoutHandler's docs to match its new interfaces

[gopherbot]

Change https://golang.org/cl/191169 mentions this issue: [release-branch.go1.13] net/http: change TimeoutHandler's docs to match its new interfaces