x/net/http2: window updates on randomWriteScheduler after stream closed cause memory leaks [1.13 backport]

[gopherbot]

@bradfitz requested issue #33812 to be considered for backport to the next 1.13 minor release.

@jared2501, thanks for the great bug report & diagnosis!

@gopherbot, please backport to Go 1.13.

/cc @tombergan

[bradfitz]

@andybons, @bcmills, okay for backport?

[gopherbot]

Change https://golang.org/cl/198617 mentions this issue: [release-branch.go1.13] http2: fix memory leak in random write scheduler

[gopherbot]

Closed by merging 7ce5fdcd922f5ff36c5692af8042450629e41b3c to release-branch.go1.13.

[gopherbot]

Change https://golang.org/cl/198897 mentions this issue: [release-branch.go1.13] net/http: update bundled http2 for memory leak fix