Revert "Merge pull request Z-Hub#95 from matidau/imap-as16"

This reverts commit 555320f, reversing
changes made to 7a4702d.

src/backend/imap/imap.php

@@ -1990,7 +1990,7 @@ public function Settings($settings) {
      * @return string       AS version constant
      */
     public function GetSupportedASVersion() {
-        return ZPush::ASV_161;
+        return ZPush::ASV_14;
     }