[scheck] fix use of undefined variable false positive in short lambda

Summary:
the semantic of short lambda is different from the legacy one, you
don't need to use 'use'. Enclosing variables are automatically
accessible (as in other languages).

Test Plan:
unit tests included
make tests

Reviewers: andrewparoski, jdelong, julienv, jcreed

Reviewed By: jdelong

CC: cparry, bryano

Differential Revision: https://phabricator.fb.com/D1159957
[spatch] fix bug with trailing comma

Test Plan: unit test included

Reviewers: amenghra, jcreed

Reviewed By: amenghra

CC: kdelong, claudiu, bryano

Differential Revision: https://phabricator.fb.com/D1160868

Task ID: 3676113