removed duplicated test

Former-commit-id: a2d9f4601bbb79124f28ec100dbdfdd2fc77c5fd

lib/single-file/single-file-core.js

@@ -857,10 +857,8 @@ this.singlefile.lib.core = this.singlefile.lib.core || (() => {
 					let stylesheetContent = await getStylesheetContent(element, this.baseURI, options, this.workStyleElement);
 					const match = stylesheetContent.match(/^@charset\s+"([^"]*)";/i);
 					if (match && match[1] && match[1] != options.charset) {
-						if (match && match[1] && match[1] != options.charset) {
-							options.charset = match[1];
-							stylesheetContent = await getStylesheetContent(element, this.baseURI, options, this.workStyleElement);
-						}
+						options.charset = match[1];
+						stylesheetContent = await getStylesheetContent(element, this.baseURI, options, this.workStyleElement);
 					}
 					let stylesheet;
 					try {