Revert of add ganesh checkbox to skfiddle interface (patchset #6 id:270001 of https://codereview.chromium.org/649313002/)

Reason for revert:
adding -Dskia_mesa=1 broke production; don't yet know why and don't want to leave things in a broken state.

Original issue's description:
> add ganesh checkbox to skfiddle interface
>
> BUG=skia:
> R=mtklein@google.com, tfarina@chromium.org
>
> Committed: https://skia.googlesource.com/skia/+/ccb54895c614632fd01d22b64ab614921f980eb1

TBR=tfarina@chromium.org,jcgregorio@google.com,mtklein@google.com
NOTREECHECKS=true
NOTRY=true
BUG=skia:

Review URL: https://codereview.chromium.org/655633003