Remove hard coded single quotes in arc feature

Summary:
Single quotes aren't valid in the windows cmd prompt, so arc feature
didn't work in mercurial when it got to this line.

I have no idea why %C was used before.  Nothing in that string should be
broken by the escaping.

Test Plan:
Ran arc feature --trace on my mac. Verified the command was escaped correctly
and the correct feature results were printed.

I don't have a windows machine to try it on, but the builtin escaping should
now account for windows machines.

Reviewers: epriestley

Reviewed By: epriestley

CC: sid0, aran, Korvin

Differential Revision: https://secure.phabricator.com/D6637

src/workflow/ArcanistFeatureWorkflow.php

@@ -179,7 +179,7 @@ EOTEXT
     foreach ($branches as $branch) {
       if ($repository_api instanceof ArcanistMercurialAPI) {
         $futures[$branch['name']] = $repository_api->execFutureLocal(
-          "log -l 1 --template '%C' -r %s",
+          "log -l 1 --template %s -r %s",
           "{node}\1{date|hgdate}\1{p1node}\1{desc|firstline}\1{desc}",
           hgsprintf('%s', $branch['name']));