Update params.env with caikit standalone

Signed-off-by: Christina Xu <chrxu@redhat.com>

config/base/params.env

@@ -1,5 +1,6 @@
 odh-model-controller=quay.io/opendatahub/odh-model-controller:v0.12.0-latest
 caikit-tgis-image=quay.io/opendatahub/caikit-tgis-serving:stable-01d6d99
+caikit-standalone-image=quay.io/modh/caikit-nlp:stable-994ec60
 tgis-image=quay.io/opendatahub/text-generation-inference:stable-ed9d828
 ovms-image=quay.io/opendatahub/openvino_model_server:stable-nightly-2024-05-26
 vllm-image=quay.io/opendatahub/vllm:stable-affc486