chore(DAGs): Remove deprecated sft, rl, and gemma3-4b e2e DAGs (GoogleCloudPlatform#1303)

This change removes the following deprecated DAGs in accordance with b/528415968, b/528424941, and b/528418808:
- `maxtext_sft.py`
- `maxtext_rl.py`
- `maxtext_sft_notebook.py`
- `maxtext_rl_notebook.py`
- Gemma3-4b from `maxtext_end_to_end.py`

Author: chiajunglien

dags/common/scheduling_helper/dag_integrity_whitelist.yaml

@@ -75,10 +75,6 @@ whitelisted_dags:
 - maxtext_regular_restore_with_node_disruption
 - maxtext_regular_restore_with_resumed_workload
 - maxtext_regular_save
-- maxtext_rl
-- maxtext_rl_notebook
-- maxtext_sft
-- maxtext_sft_notebook
 - maxtext_sft_trainer
 - maxtext_sweep_gke_example_dag
 - maxtext_trillium_configs_perf

dags/multipod/maxtext_end_to_end.py

@@ -69,14 +69,6 @@
               "bash tests/end_to_end/tpu/gemma2/2b/test_gemma2_to_hf.sh",
           ],
       },
-      "gemma3-4b": {
-          "owner": test_owner.HENGTAO_G,
-          "commands": [
-              "export RUN_NAME=$(date +%Y-%m-%d-%H-%M-%S)",
-              "bash tests/end_to_end/tpu/gemma3/4b/test_gemma3_to_mt.sh $RUN_NAME",
-              "bash tests/end_to_end/tpu/gemma3/4b/test_gemma3.sh $RUN_NAME",
-          ],
-      },
       "qwen3-4b": {
           "owner": test_owner.HENGTAO_G,
           "commands": [