Set flux test as optional (#14190)

Signed-off-by: Charlie Truong <[email protected]>

Author: chtruong814

.github/workflows/cicd-main-nemo2.yml

@@ -270,6 +270,7 @@ jobs:
             script: L2_NeMo_2_Diffusion_Taskencoder_Test
           - runner: self-hosted-azure
             script: L2_NeMo_2_Flux_Import_Test
+            is-optional: true
           - runner: self-hosted-azure
             script: L2_NeMo_2_Flux_Inference_Test
           - runner: self-hosted-azure