Cancel autocomplete on "{" and "}"

Summary: Ref T10163. These are almost certainly not username/project characters, and are fairly likely to be `@{...}` Diviner references.

Test Plan: Typed `@{...`, no more autocomplete.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T10163

Differential Revision: https://secure.phabricator.com/D15110

webroot/rsrc/js/phuix/PHUIXAutocomplete.js

@@ -333,7 +333,7 @@ JX.install('PHUIXAutocomplete', {
     _getCancelCharacters: function() {
       // The "." character does not cancel because of projects named
       // "node.js" or "blog.mycompany.com".
-      return ['#', '@', ',', '!', '?'];
+      return ['#', '@', ',', '!', '?', '{', '}'];
     },
 
     _getTerminators: function() {