bug: acme challenge http01 doen't resolve on merged-eg

*Description*:

Resolver pod of acme http01 challenge doesn't resolve when referencing the merged-eg. The expected SSL certificate isn't issued.

*Repro steps*:

1. Setup [merged-eg](https://gateway.envoyproxy.io/docs/tasks/operations/deployment-mode/#merged-gateways-deployment) example
2. Setup [cert-manager](https://gateway.envoyproxy.io/docs/tasks/security/tls-cert-manager/) example
3. Change `ClusterIssuer` spec to `spec.acme.solvers.http01.gatewayHTTPRoute.parentRefs.name: merged-eg`

*Environment*:

Envoy Version: v1.3.0
Cert-Manager: v1.17.0
K8s: 1.32.2

*Logs*:

Apparently none.