Issue #3460832: Replace fake SVG icon to proper vector graphics

Closes #3460832

js/ckeditor5_plugins/drupalentity/entity.svg

-<?xml version="1.0" encoding="UTF-8" standalone="no"?>
-<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
-<svg version="1.1" id="Layer_1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" x="0px" y="0px" width="16px" height="16px" viewBox="0 0 16 16" enable-background="new 0 0 16 16" xml:space="preserve">  <image id="image0" width="16" height="16" x="0" y="0"
-    href="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABAAAAAQCAQAAAC1+jfqAAAABGdBTUEAALGPC/xhBQAAAAJiS0dE
-AP+Hj8y/AAAAB3RJTUUH5gkNAywZrK+VpAAAAElJREFUKM9jYKAeuMrwHwUuhwizoCj6xfALzv6J
-zYRKTIOZCNmMaoUpQzKcvZnhFX5HWmIz4SrDDTj7LbUcSVABbkfeJ9kEcgEApvsllE2X4VkAAAAl
-dEVYdGRhdGU6Y3JlYXRlADIwMjItMDktMTNUMDE6NDQ6MjUrMDI6MDCMUacyAAAAJXRFWHRkYXRl
-Om1vZGlmeQAyMDIyLTA5LTEzVDAxOjQ0OjI1KzAyOjAw/QwfjgAAAABJRU5ErkJggg==" />
-</svg>
+<svg xmlns="http://www.w3.org/2000/svg" xml:space="preserve" viewBox="0 0 16 16"><path d="M4 2.5h8v1.8H5.8V7h4.7v2H5.8v2.7H12v1.8H4z"/></svg>