Only call ::checkForVisibilityChange on editor attachment, not ::pollDOM

I’m pretty sure ::pollDOM is subsumed by ::checkForVisibilityChange
because there’s no reason the editor would be considered visible prior
to being attached.

src/editor-view.coffee

@@ -143,10 +143,6 @@ class EditorView extends View
     return unless onDom
     return if @attached
     @attached = true
-    @component.pollDOM()
-
-    # Ensure that editor measurements like lineHeight are taken here, even if pollDOM() was a no-op
-    # because an update was requested.
     @component.checkForVisibilityChange()
 
     @focus() if @focusOnAttach