Ignore commit upgrades for otel-go in renovate (#6144)

We often have unstable packages relying on a commit of otel-go
temporarily, to spee up development.
That gives us very frequent renovate PRs (for every commit in otel-go),
that we don't really need.

See #6142

This PR proposes to get renovate to only upgrade otel-go for releases
matching semantic versions, so we don't upgrade every commit anymore.

---------

Co-authored-by: Robert Pająk <[email protected]>

renovate.json

@@ -25,6 +25,10 @@
     {
       "matchPackageNames": ["google.golang.org/genproto/googleapis/**"],
       "groupName": "googleapis"
+    },
+    {
+      "matchPackageNames": ["go.opentelemetry.io/otel/**"],
+      "allowedVersions": "/^v[0-9]+\\.[0-9]+\\.[0-9]+/"
     }
   ]
 }