go/vcs: fix doc typos
go/vcs: fix doc typos

Change-Id: Ife1f9534d08d3bd9beeb4e6e798733d71e6f72b5
Reviewed-on: https://go-review.googlesource.com/15750
Reviewed-by: Dmitri Shuralyov <0c2a7749d909c8353e59c3f9c6a4d19a5ce000c1@gmail.com>
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

cmars/tools,syreclabs/go-tools,cmars/tools,golang/tools,golang/tools,syreclabs/go-tools,golang/tools,syreclabs/go-tools,syreclabs/go-tools,golang/tools,cmars/tools,cmars/tools,syreclabs/go-tools,golang/tools,syreclabs/go-tools