os: remove 5ms exec sleep on Windows

[bradfitz]

src/os/exec_windows.go contains in its (*Process).wait method:

	// NOTE(brainman): It seems that sometimes process is not dead
	// when WaitForSingleObject returns. But we do not know any
	// other way to wait for it. Sleeping for a while seems to do
	// the trick sometimes. So we will sleep and smell the roses.
	defer time.Sleep(5 * time.Millisecond)

That is unfortunate.

I tried to remove it on https://go-review.googlesource.com/c/go/+/84175 specifically for debugging Windows XP problems (#2866 and #17245), and it apparently didn't work.

But we don't support Windows XP anymore, so maybe we can remove it now?

But I forget everything about Windows I had learned while researching that patch, so opening this bug instead.

/cc @alexbrainman @jordanrh1

[agnivade]

You had opened the exact same bug here - #25965. An oversight perhaps ?

[bradfitz]

@agnivade, ah, thanks! Closing this one.