Mark some methods in `ArcanistLinter` as final
Mark some methods in `ArcanistLinter` as final

Summary: Minor change, self-explanatory... this seems to make sense.

Test Plan: N/A

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D10476

haskell-infra/arcanist,haskell-infra/arcanist,haskell-infra/arcanist,kevinseelbach/arcanist,calblueprint/arcanist,phacility/arcanist,KieranHayes/arcanist,Khan/arcanist,folsom-labs/arcanist,codelabs-ch/arcanist,Khan/arcanist,hach-que/arcanist,hach-que/arcanist,codelabs-ch/arcanist,sneakpeeq/arcanist,fivestars/arcanist,zhihu/arcanist,Symplicity/arcanist,aik099/arcanist,PageUpPeopleOrg/arcanist-patches,Symplicity/arcanist,r4nt/arcanist,KieranHayes/arcanist,Symplicity/arcanist,PageUpPeopleOrg/arcanist-patches,wharris/arcanist,codelabs-ch/arcanist,aik099/arcanist,phacility/arcanist,Khan/arcanist,kevinseelbach/arcanist,jra3/arcanist,eSpark/arcanist,folsom-labs/arcanist,sneakpeeq/arcanist,aik099/arcanist,fivestars/arcanist,fivestars/arcanist,wikimedia/phabricator-arcanist,aik099/arcanist,Symplicity/arcanist,wikimedia/phabricator-arcanist,fivestars/arcanist,alexmv/arcanist,calblueprint/arcanist,zhihu/arcanist,memsql/arcanist,coursera/arcanist,jra3/arcanist,folsom-labs/arcanist,coursera/arcanist,chundongwang/arcanist,chundongwang/arcanist,memsql/arcanist,sneakpeeq/arcanist,wxstars/arcanist,uber/arcanist,uber/arcanist,wxstars/arcanist,uber/arcanist,r4nt/arcanist,wharris/arcanist,wikimedia/phabricator-arcanist,haskell-infra/arcanist,folsom-labs/arcanist,calblueprint/arcanist,eSpark/arcanist,kevinseelbach/arcanist,jra3/arcanist,eSpark/arcanist,eSpark/arcanist,wxstars/arcanist,wharris/arcanist,PageUpPeopleOrg/arcanist-patches,r4nt/arcanist,r4nt/arcanist,KieranHayes/arcanist,memsql/arcanist,kevinseelbach/arcanist,coursera/arcanist,wikimedia/phabricator-arcanist,wharris/arcanist,calblueprint/arcanist,uber/arcanist,chundongwang/arcanist,zhihu/arcanist,sneakpeeq/arcanist,wxstars/arcanist,codelabs-ch/arcanist,hach-que/arcanist,phacility/arcanist,KieranHayes/arcanist,codelabs-ch/arcanist,zhihu/arcanist,PageUpPeopleOrg/arcanist-patches,memsql/arcanist,alexmv/arcanist,Khan/arcanist,chundongwang/arcanist,alexmv/arcanist,phacility/arcanist,phacility/arcanist,coursera/arcanist,jra3/arcanist,alexmv/arcanist,hach-que/arcanist