remove \\9 at the end of property values

lib/single-file/modules/css-fonts-alt-minifier.js

@@ -243,7 +243,7 @@ this.singlefile.lib.modules.fontsAltMinifier = this.singlefile.lib.modules.fonts
 		}
 		if (property) {
 			try {
-				return cssTree.generate(property.data.value);
+				return cssTree.generate(property.data.value).replace(/\\9$/, "");
 			} catch (error) {
 				// ignored
 			}