Remove processPreKey from protocol_wrapper

Use SessionBuilder directly instead of protocol_wrapper

// FREEBIE

libtextsecure/protocol_wrapper.js

@@ -76,13 +76,6 @@
                     throw e;
                 });
             });
-        },
-        processPreKey: function(preKeyBundle) {
-            return queueJobForNumber(preKeyBundle.encodedNumber, function() {
-                var address = libsignal.SignalProtocolAddress.fromString(preKeyBundle.encodedNumber);
-                var builder = new libsignal.SessionBuilder(textsecure.storage.protocol, address);
-                return builder.processPreKey(preKeyBundle);
-            });
         }
     };
 })();