Renovate config: forbid updating to kotest ...-LOCAL (#248)

The `6.0.0-LOCAL` version shouldn't have been published to the Gradle
Plugin Portal, but since it's there, we don't want to update to it
because it's missing some artifacts.

Following
https://docs.renovatebot.com/configuration-options/#ignore-versions-with-negated-regex-syntax

Author: krzema12

renovate.json

@@ -3,5 +3,11 @@
   "extends": [
     "config:base"
   ],
-  "automerge": true
+  "automerge": true,
+  "packageRules": [
+    {
+      "matchPackageNames": ["io.kotest.multiplatform"],
+      "allowedVersions": "!/LOCAL$/"
+    }
+  ]
 }