Remove unused `@noCallThru` object properties

This used to have an effect when we used proxyquire for mocking. It does
nothing now.

src/annotator/test/guest-test.coffee

@@ -4,7 +4,6 @@ Plugin = require('../plugin')
 
 Delegator = require('../delegator')
 $ = require('jquery')
-Delegator['@noCallThru'] = true
 
 Guest = require('../guest')
 { $imports } = require('../guest')
@@ -12,7 +11,6 @@ rangeUtil = null
 selections = null
 
 scrollIntoView = sinon.stub()
-scrollIntoView['@noCallThru'] = true
 
 class FakeAdder
   instance: null

src/sidebar/util/test/is-third-party-service-test.js

@@ -11,7 +11,6 @@ describe('sidebar.util.isThirdPartyService', () => {
 
     $imports.$mock({
       '../service-config': fakeServiceConfig,
-      '@noCallThru': true,
     });
   });