Fixed that selector pattern can take exponential time (#1499)

Fixes #1498.

Author: RunDevelopment

components/prism-scss.js

@@ -21,7 +21,7 @@ Prism.languages.scss = Prism.languages.extend('css', {
 	// this one was hard to do, so please be careful if you edit this one :)
 	'selector': {
 		// Initial look-ahead is used to prevent matching of blank selectors
-		pattern: /(?=\S)[^@;{}()]?(?:[^@;{}()]|&|#\{\$[-\w]+\})+(?=\s*\{(?:\}|\s|[^}]+[:{][^}]+))/m,
+		pattern: /(?=\S)[^@;{}()]?(?:[^@;{}()]|#\{\$[-\w]+\})+(?=\s*\{(?:\}|\s|[^}]+[:{][^}]+))/m,
 		inside: {
 			'parent': {
 				pattern: /&/,
@@ -72,4 +72,4 @@ Prism.languages.insertBefore('scss', 'function', {
 	}
 });
 
-Prism.languages.scss['atrule'].inside.rest = Prism.languages.scss;
+Prism.languages.scss['atrule'].inside.rest = Prism.languages.scss;