fix typo

public/app/core/utils/kbn.js

@@ -171,7 +171,7 @@ function($, _) {
   kbn.describe_interval = function (string) {
     var matches = string.match(kbn.interval_regex);
     if (!matches || !_.has(kbn.intervals_in_seconds, matches[2])) {
-      throw new Error('Invalid interval string, expexcting a number followed by one of "Mwdhmsy"');
+      throw new Error('Invalid interval string, expecting a number followed by one of "Mwdhmsy"');
     } else {
       return {
         sec: kbn.intervals_in_seconds[matches[2]],