Revert vLLM GPU Image Tags

https://github.com/kubernetes-sigs/gateway-api-inference-extension/pull/1453 and https://github.com/kubernetes-sigs/gateway-api-inference-extension/pull/1479 reverted the vLLM GPU image from `latest`/`0.9.2` respectivly to `0.8.5` due to https://github.com/vllm-project/vllm/issues/19184. Revert these changes when the upstream bug is fixed in a published vLLM image.