ETL descriptions too long

Such a long test is really a comment, not a description to be used as a test identifier.
Make it so, per #1473

Author: bencoman

exercises/etl/canonical-data.json

@@ -10,7 +10,10 @@
         "such that keys are integers. e.g. in JavaScript, it might look ",
         "like `transform( { 1: ['A'] } );`"
       ],
-      "description": "transforms the a set of scrabble data previously indexed by the tile score to a set of data indexed by the tile letter",
+      "description": "Transform",
+      "comments": [ "Transforms the a set of scrabble data previously indexed by the tile score",
+                    "to a set of data indexed by the tile letter"
+      ],
       "cases": [
         {
           "description": "a single letter",