Remove some now-unnecessary msvs_cygwin_shell:1

These might (?) have been necessary for VS builds, but we don't need
them any longer.

TBR=vsevik@chromium.org
R=thakis@chromium.org
BUG=123026
TEST=remove outputs and ninja -C out\Debug associated target

Review URL: https://codereview.chromium.org/136793031

git-svn-id: svn://svn.chromium.org/blink/trunk@165482 bbb929c8-8fbe-4397-9dbb-9b2b20218538