Filter comments by content instead of actor (#519)

* Filter comments by content instead of actor

* Remove dead actor code

* WIP fix tests

* Fix test

__tests__/milestones.spec.ts

@@ -39,7 +39,6 @@ describe('milestones options', (): void => {
   const setProcessor = () => {
     processor = new IssuesProcessorMock(
       opts,
-      async () => 'abot',
       async p => (p === 1 ? testIssueList : []),
       async () => [],
       async () => new Date().toDateString()