Fix params reference for default_constraints_branch (#26406)

Fixes breeze commands that depends on the default constraints branch,
such as the generated diff for
`breeze release-management generate-constraints`

Author: gmsantos

dev/breeze/src/airflow_breeze/utils/docker_command_utils.py

@@ -610,7 +610,7 @@ def update_expected_environment_variables(env: dict[str, str]) -> None:
     "AIRFLOW_CI_IMAGE": "airflow_image_name",
     "AIRFLOW_CI_IMAGE_WITH_TAG": "airflow_image_name_with_tag",
     "AIRFLOW_EXTRAS": "airflow_extras",
-    "DEFAULT_CONSTRAINTS_BRANCH": "default-constraints-branch",
+    "DEFAULT_CONSTRAINTS_BRANCH": "default_constraints_branch",
     "AIRFLOW_CONSTRAINTS_MODE": "airflow_constraints_mode",
     "AIRFLOW_CONSTRAINTS_REFERENCE": "airflow_constraints_reference",
     "AIRFLOW_IMAGE_KUBERNETES": "airflow_image_kubernetes",