Remove ES6 from ddp-client (#8516)

Follow-up to 05be2c784c which added new ES6 syntax, but failed to add `ecmascript`.

* Remove ecmascript Object function shorthand notation.
   as the `rate-limit` package doesn't currently use `ecmacsript` and using it for just this one instance of ES6 isn't worth it.
* Remove `ecmascript` from `rate-limit` as it is now unused.
* Bump `rate-limit` version in preparation for publishing.
Fixes #8515

packages/rate-limit/package.js

@@ -1,6 +1,6 @@
 Package.describe({
   name: 'rate-limit',
-  version: '1.0.7',
+  version: '1.0.8',
   // Brief, one-line summary of the package.
   summary: 'An algorithm for rate limiting anything',
   // URL to the Git repository containing the source code for this package.

packages/rate-limit/rate-limit.js

@@ -102,7 +102,7 @@ _.extend(Rule.prototype, {
     self.counters = {};
     self._lastResetTime = new Date().getTime();
   },
-  _executeCallback(reply, ruleInput) {
+  _executeCallback: function (reply, ruleInput) {
     try {
       if (this.options.callback) {
         this.options.callback(reply, ruleInput);