os/exec: docs bugs sections points to an issue with unsupported OS version

[rajender]

https://golang.org/pkg/os/exec/#pkg-note-BUG points to a bug which exists in an unsupported macosx version 10.6 only (I suppose). (https://github.com/golang/go/wiki/MinimumRequirements)

Should this be removed?

[bradfitz]

SGTM. I sent a change.

[gopherbot]

CL https://golang.org/cl/45171 mentions this issue.