cmd/go: fix typo in comment
cmd/go: fix typo in comment

Fixes issue 4432.

R=golang-dev, minux.ma
CC=golang-dev
http://codereview.appspot.com/6858064

mhennings/marcohennings-go,d0f/go-zh,rflanagan/reginaldflanagan-project1,glycerine/jeaten-go-arrayof-structof,bryanxu/go-zh,sanjosh/sanjos100-tipc,webfd/go-zh,rdp/rogerpack2005-golang,scirelli/scirelli-go,mhennings/marcohennings-go,sanjosh/sanjos100-tipc,sanjosh/sanjos100-tipc,scirelli/scirelli-go,scirelli/scirelli-go,rdp/rogerpack2005-golang,rflanagan/reginaldflanagan-project1,sanjosh/sanjos100-tipc,rflanagan/reginaldflanagan-project1,bryanxu/go-zh,webfd/go-zh,rflanagan/reginaldflanagan-project1,sanjosh/sanjos100-tipc,rdp/rogerpack2005-golang,glycerine/jeaten-go-arrayof-structof,bryanxu/go-zh,d0f/go-zh,rflanagan/reginaldflanagan-project1,glycerine/jeaten-go-arrayof-structof,scirelli/scirelli-go,d0f/go-zh,d0f/go-zh,webfd/go-zh,glycerine/jeaten-go-arrayof-structof,rdp/rogerpack2005-golang,scirelli/scirelli-go,scirelli/scirelli-go,webfd/go-zh,sanjosh/sanjos100-tipc,mhennings/marcohennings-go,glycerine/jeaten-go-arrayof-structof,d0f/go-zh,bryanxu/go-zh,rdp/rogerpack2005-golang,glycerine/jeaten-go-arrayof-structof,sanjosh/sanjos100-tipc,mhennings/marcohennings-go,mhennings/marcohennings-go,mhennings/marcohennings-go,rflanagan/reginaldflanagan-project1,scirelli/scirelli-go,bryanxu/go-zh,bryanxu/go-zh,bryanxu/go-zh,webfd/go-zh,sanjosh/sanjos100-tipc,rdp/rogerpack2005-golang,webfd/go-zh,glycerine/jeaten-go-arrayof-structof,rflanagan/reginaldflanagan-project1,webfd/go-zh,d0f/go-zh,glycerine/jeaten-go-arrayof-structof,rdp/rogerpack2005-golang,scirelli/scirelli-go,d0f/go-zh,rdp/rogerpack2005-golang,webfd/go-zh,bryanxu/go-zh,d0f/go-zh,rflanagan/reginaldflanagan-project1,mhennings/marcohennings-go,mhennings/marcohennings-go