Fix dockerfile to pin to Gel 6.4 as well

Author: CarsonF

Dockerfile

@@ -1,6 +1,6 @@
 ARG NODE_VERSION=22
 ARG NODE_IMAGE=public.ecr.aws/docker/library/node:${NODE_VERSION}-slim
-ARG GEL_IMAGE=ghcr.io/geldata/gel:6
+ARG GEL_IMAGE=ghcr.io/geldata/gel:6.4
 
 FROM ${NODE_IMAGE} AS base-runtime