Enforce property shorthand (#2243)

I had to track down the right lint rule for this. We have no-useless-rename for destructuring and import/export. The one for object literals is object-shorthand.

services/gem/gem-downloads.service.js

@@ -41,7 +41,7 @@ module.exports = class GemDownloads extends BaseJsonService {
 
   static render({ label, downloads }) {
     return {
-      label: label,
+      label,
       message: metric(downloads),
       color: downloadCountColor(downloads),
     }

services/gem/gem-rank.service.js

@@ -41,7 +41,7 @@ module.exports = class GemRank extends BaseJsonService {
     let message = ordinalNumber(rank)
     message += period === 'rt' ? '' : ' daily'
     return {
-      message: message,
+      message,
       color: floorCountColor(count, 10, 50, 100),
     }
   }