Update the sarif schema file

The version we were using is quite old. Copied the latest from
https://github.com/oasis-tcs/sarif-spec/blob/123e95847b13fbdd4cbe2120fa5e33355d4a042b/Schemata/sarif-schema-2.1.0.json

I do not think the sarif spec will be changing any more without
an explicit version update, so this is fine for now.

Author: aeisenberg