don't remove existing fonts from the cache

lib/single-file/font-face-proxy.js

@@ -28,7 +28,6 @@ this.fontFaceProxy = this.fontFaceProxy || (() => {
 			featureSettings: "font-feature-settings"
 		};
 
-		Array.from(document.fonts).forEach(fontFace => document.fonts.delete(fontFace));
 		const FontFace = window.FontFace;
 		window.__defineGetter__("FontFace", () => new Proxy(FontFace, {
 			construct(FontFace, argumentsList) {