feat(deps): update-json using discovery API

Instead of depending on the google go client API repository, I now
use the original data source, namely the discovery API.

fixes #5

etc/api/groupsmigration/v1/groupsmigration-api.json

@@ -1,6 +1,6 @@
 {
  "kind": "discovery#restDescription",
- "etag": "\"FrPV2U6xXFUq8eRv_PO3IoAURkc/uMvgRqCygYBIh2d3lXb4f8cUWOw\"",
+ "etag": "\"ye6orv2F-1npMW3u9suM3a7C5Bo/uMvgRqCygYBIh2d3lXb4f8cUWOw\"",
  "discoveryVersion": "v1",
  "id": "groupsmigration:v1",
  "name": "groupsmigration",