Remove broken linter

Summary: It is broken.

Reviewers: bgamari

Reviewed By: bgamari

Differential Revision: https://phabricator.haskell.org/D3118

Author: mpickering

Diff for: .arclint

@@ -35,10 +35,6 @@
       "type": "phutil-library",
       "include": "(\\.php$)"
     },
-    "phutil-xhpast": {
-      "type": "phutil-xhpast",
-      "include": "(^\\.php$)"
-    },
     "xhpast": {
       "type": "xhpast",
       "include": "(\\.php$)"