git: Only enable the registry shortcuts

The cheetah extension is causing issues when ssh-agent is running.
See https://github.com/msysgit/msysgit/issues/249 and https://github.com/ferventcoder/chocolatey-packages/pull/36 for more information.
git: Fix 93cc64e - Add the start-menu icons by default

Due to a wrong reaction with personal work overload (I never know when to stop),
I had lacked of concentration and seriousness when writing commit 93cc64e.

It resulted in coding the exact opposite of what I wanted.

Things should now work as expected.