Fix spelling

Summary: Noticed a couple of typos in the docs, and then things got out of hand.

Test Plan:
  - Stared at the words until my eyes watered and the letters began to swim on the screen.
  - Consulted a dictionary.

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: epriestley, yelirekim, PHID-OPKG-gm6ozazyms6q6i22gyam

Differential Revision: https://secure.phabricator.com/D18693

src/applications/auth/controller/PhabricatorAuthController.php

@@ -134,7 +134,7 @@ abstract class PhabricatorAuthController extends PhabricatorController {
     // checks later on to make sure this account is valid for the intended
     // operation. This requires edit permission for completeness and consistency
     // but it won't actually be meaningfully checked because we're using the
-    // ominpotent user.
+    // omnipotent user.
 
     $account = id(new PhabricatorExternalAccountQuery())
       ->setViewer(PhabricatorUser::getOmnipotentUser())