remove MAXDIFFUSION_GPU_JAX_STABLE image and related DAG for GPU tests (GoogleCloudPlatform#1195)

Author: michelle-yooh

dags/common/vm_resource.py

@@ -367,9 +367,6 @@ class DockerImage(enum.Enum):
       "gcr.io/tpu-prod-env-multipod/maxdiffusion_jax_stable_stack:"
       f"{datetime.datetime.today().strftime('%Y-%m-%d')}"
   )
-  MAXDIFFUSION_GPU_JAX_STABLE = (
-      "gcr.io/tpu-prod-env-multipod/maxdiffusion_jax_stable_gpu:latest"
-  )
   MAXDIFFUSION_TPU_STABLE_STACK_NIGHTLY_JAX = (
       "gcr.io/tpu-prod-env-multipod/maxdiffusion_jax_stable_stack_nightly:"
       f"{datetime.datetime.today().strftime('%Y-%m-%d')}"