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/diffusion/controller/DiffusionCommitController.php

@@ -479,7 +479,7 @@ final class DiffusionCommitController extends DiffusionController {
     // chains of events). This should be rare, but does not indicate a bug
     // or data issue.
 
-    // NOTE: We never query push logs in SVN because the commiter is always
+    // NOTE: We never query push logs in SVN because the committer is always
     // the pusher and the commit time is always the push time; the push log
     // is redundant and we save a query by skipping it.