go.tools/dashboard: remove Solaris builders from flaky builders list
go.tools/dashboard: remove Solaris builders from flaky builders list

solaris-amd64-solaris11 has been the most stable builder,
by far, over the last 9 months. solaris-amd64-smartos is
stable too and it's our fastest builder.

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=adg, dave, golang-codereviews
https://codereview.appspot.com/163280043

karmakaze/go.tools,karmakaze/go.tools,karmakaze/go.tools,karmakaze/go.tools,karmakaze/go.tools