🔧 configure renovate to deduplicate subdependencies (#2643)

I chose the "highest" strategy (instead of "fewest"), because:
* let's try to be as much up-to-date as possible
* renovate will use the official `yarn dedupe` instead of a third party
  package

renovate.json

@@ -12,6 +12,7 @@
   "prConcurrentLimit": 5,
   "prHourlyLimit": 1,
   "schedule": ["every weekend"],
+  "postUpdateOptions": ["yarnDedupeHighest"],
   "packageRules": [
     {
       "groupName": "all non-major dependencies",