go.tools/go/ssa: remove windows test exclusion
go.tools/go/ssa: remove windows test exclusion

Issue 7189 was likely fixed with revision ed6ecfe1bc4e .

LGTM=adonovan
R=adonovan
CC=golang-codereviews
https://codereview.appspot.com/59230044

d0f/go-zh.tools,skyportsystems/go.tools,skyportsystems/go.tools,webfd/go-zh.tools,webfd/go-zh.tools,bryanxu/go-zh.tools,skyportsystems/go.tools,bryanxu/go-zh.tools,d0f/go-zh.tools,d0f/go-zh.tools,8limbs/gotools,skyportsystems/go.tools,8limbs/gotools,skyportsystems/go.tools,bryanxu/go-zh.tools,bryanxu/go-zh.tools,bryanxu/go-zh.tools,webfd/go-zh.tools,8limbs/gotools,webfd/go-zh.tools,webfd/go-zh.tools,d0f/go-zh.tools,d0f/go-zh.tools