doc: fix installation $GOOS choices
doc: fix installation $GOOS choices

The $GOOS choices text and combinations list should match.

R=adg
CC=golang-dev
http://codereview.appspot.com/3485046

Committer: Andrew Gerrand <395a7d33bec8475c9b83b7d440f141bcbd994aa5@golang.org>

h8liu/golang,pombredanne/go-deleteme,h8liu/golang,apparentlymart/golang,ssrl/go,dsriram/golang,apparentlymart/golang,ssrl/go,apparentlymart/golang,pombredanne/go-deleteme,gnanderson/go,dsriram/golang,ssrl/go,gnanderson/go,gnanderson/go,pombredanne/go-deleteme,ssrl/go,ssrl/go,h8liu/golang,h8liu/golang,h8liu/golang,dsriram/golang,pombredanne/go-deleteme,gnanderson/go,pombredanne/go-deleteme,h8liu/golang,apparentlymart/golang,pombredanne/go-deleteme,gnanderson/go,dsriram/golang,tv42/old-go,dsriram/golang,apparentlymart/golang,gnanderson/go,ssrl/go,dsriram/golang,tv42/old-go,tv42/old-go,tv42/old-go,tv42/old-go,tv42/old-go,tv42/old-go,dsriram/golang,h8liu/golang,apparentlymart/golang,apparentlymart/golang,ssrl/go,gnanderson/go,pombredanne/go-deleteme