Use a less-esoteric spelling of "capabilities" in several places

Summary: This spelling can definitely feel a little overplayed at times, but I still think it's a gold standard in spellings of "capabilities".

Test Plan: Felt old and uncool.

Reviewers: chad

Reviewed By: chad

Differential Revision: https://secure.phabricator.com/D18215

src/applications/diffusion/protocol/DiffusionMercurialWireProtocol.php

@@ -105,14 +105,14 @@ final class DiffusionMercurialWireProtocol extends Phobject {
    * disallow the client from knowing we speak bundle2 by removing it
    * from the capabilities listing.
    *
-   * The format of the capabilties string is: "a space separated list
+   * The format of the capabilities string is: "a space separated list
    * of strings representing what commands the server supports"
    * @link https://www.mercurial-scm.org/wiki/CommandServer#Protocol
    *
    * @param string  $capabilities - The string of capabilities to
    *   strip the bundle2 capability from. This is expected to be
    *   the space-separated list of strings resulting from the
-   *   querying the 'capabilties' command.
+   *   querying the 'capabilities' command.
    *
    * @return string  The resulting space-separated list of capabilities
    *   which no longer contains the 'bundle2' capability. This is meant

src/applications/policy/controller/PhabricatorPolicyExplainController.php

@@ -253,7 +253,7 @@ final class PhabricatorPolicyExplainController
       ->appendParagraph(
         pht(
           'To access this object, users must have first have access '.
-          'capabilties on these other objects:'))
+          'capabilities on these other objects:'))
       ->appendList($items);
   }