Don't check whether document has focus for takeFocus

Closes #4975. Checking `hasFocus` is a reasonable idea, but in Firefox
`hasFocus` returns false on `mousedown` if the window, but not the document
was focussed before. This leads to a wrong cursor in `contenteditable`
input style.

src/display/operations.js

@@ -115,7 +115,7 @@ function endOperation_W2(op) {
     cm.display.maxLineChanged = false
   }
 
-  let takeFocus = op.focus && op.focus == activeElt() && (!document.hasFocus || document.hasFocus())
+  let takeFocus = op.focus && op.focus == activeElt()
   if (op.preparedSelection)
     cm.display.input.showSelection(op.preparedSelection, takeFocus)
   if (op.updatedDisplay || op.startHeight != cm.doc.height)