docs: delete extra semicolon (#266)

README.md

@@ -33,7 +33,7 @@ npm install @postlight/mercury-parser
 ```javascript
 import Mercury from '@postlight/mercury-parser';
 
-Mercury.parse(url).then(result => console.log(result););
+Mercury.parse(url).then(result => console.log(result));
 
 // NOTE: When used in the browser, you can omit the URL argument
 // and simply run `Mercury.parse()` to parse the current page.