remove `lint.engine` from global .arcrc
remove `lint.engine` from global .arcrc

Summary:
this is now part of webapp's `.arclint` so other projects no longer
need to inherit this lint setup (but can opt into whatever sundry lint setup
they need).

depends on  https://phabricator.khanacademy.org/D18071 and part of
https://app.asana.com/0/27216215224639/34648822879713 as well as
https://app.asana.com/0/27216215224639/33266691393487

this commit will not be landed until the .arclint commit lands in webapp

Test Plan: ran arc lint on some errorful files, arc still worked

Reviewers: mroth, csilvers

Reviewed By: csilvers

Subscribers: alpert, csilvers

Projects: #devenvfixup

Differential Revision: https://phabricator.khanacademy.org/D18088

Khan/arcanist,Khan/arcanist,Khan/arcanist,Khan/arcanist