Remove unused $scope.shouldShowThread

The code that depended on this scope variable was moved into the
ThreadController in 0e2bd59. It is no longer referenced anywhere.

h/static/scripts/annotation-viewer-controller.coffee

@@ -19,8 +19,6 @@ module.exports = class AnnotationViewerController
     # to annotations loaded into the stream.
     $scope.focus = angular.noop
 
-    $scope.shouldShowThread = -> true
-
     $scope.search.update = (query) ->
       $location.path('/stream').search('q', query)
 

h/static/scripts/stream-controller.coffee

@@ -53,7 +53,4 @@ module.exports = class StreamController
     $scope.isStream = true
     $scope.sort.name = 'Newest'
     $scope.threadRoot = threading.root
-
-    $scope.shouldShowThread = (container) -> true
-
     $scope.loadMore = fetch