Fix typo in new author meta tag

_includes/header.html

@@ -3,7 +3,7 @@
 <meta name="viewport" content="width=device-width, initial-scale=1.0">
 <meta name="description" content="Bootstrap, a sleek, intuitive, and powerful mobile first front-end framework for faster and easier web development.">
 <meta name="keywords" content="HTML, CSS, JS, JavaScript, framework, bootstrap, front-end, frontend, web development">
-<meta name="author" content="Mark Otto, Jacob Thornton, and Bootstrap contibutors">
+<meta name="author" content="Mark Otto, Jacob Thornton, and Bootstrap contributors">
 
 <title>
   {% if page.title == "Bootstrap" %}