chore(renovate): drop the OpenTelemetry group, now in the central config (#349)

The Renovate bot's global config now groups go.opentelemetry.io and our own libraries (shiny, unboundsoftware) for every repo; a repo rule matching the same packages would override that grouping.

Central Renovate config: unboundsoftware/infra#1911. otelsetup: shiny/otelsetup#206.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

https://claude.ai/code/session_01H6eVuR4Yt3m7TbDTDwyZJi
Reviewed-on: #349

renovate.json

@@ -2,15 +2,5 @@
   "$schema": "https://docs.renovatebot.com/renovate-schema.json",
   "extends": [
     "config:recommended"
-  ],
-  "packageRules": [
-    {
-      "groupName": "OpenTelemetry",
-      "matchPackageNames": [
-        "go.opentelemetry.io/**",
-        "gitea.unbound.se/shiny/otelsetup",
-        "gitea.unbound.se/shiny/logging"
-      ]
-    }
   ]
 }