all: Fix reference to time repository in README
all: Fix reference to time repository in README

Change-Id: I21e409e523722883b5a4b67153db669f1f8167dd
Reviewed-on: https://go-review.googlesource.com/c/163897
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

golang/website,golang/website,golang/website,golang/website,golang/website,golang/website,golang/website