Bug 1158113: Removing two straggling error codes from Marionette

r=davehunt

--HG--
extra : rebase_source : 0ba61719dcfa99e06f34626672cbbac91c69906f

testing/marionette/error.js

@@ -196,7 +196,6 @@ this.InvalidSessionIdError = function(msg) {
   WebDriverError.call(this, msg);
   this.name = "InvalidSessionIdError";
   this.status = "invalid session id";
-  this.code = 13;
 };
 InvalidSessionIdError.prototype = Object.create(WebDriverError.prototype);
 
@@ -307,7 +306,6 @@ this.UnableToSetCookieError = function(msg) {
   WebDriverError.call(this, msg);
   this.name = "UnableToSetCookieError";
   this.status = "unable to set cookie";
-  this.code = 25;
 };
 UnableToSetCookieError.prototype = Object.create(WebDriverError.prototype);