remove redundant scheduler_lock column from dag table

[prabhusneha]

Refer GitHub issue #42258

Remove all scheduler_lock references from the codebase.

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[ephraimbuddy]

You have some conflicts. This seems like a breaking change even though the column is not used

[pierrejeambrun]

Assigning label labels and restarting the CI.

[uranusjr]

LGTM. When was this first added, by who, for what? (We can at least answer that with a git blame)

[pankajkoti]

we would also need a SQLAlchemy migration script generated using Alembic & kept in https://github.com/apache/airflow/tree/main/airflow/migrations/versions to drop this column, no?

Reference guide to generate the migration script: https://github.com/apache/airflow/blob/main/contributing-docs/13_metadata_database_updates.rst

cc: @ephraimbuddy

[ashb]

This predates airflow 2, and I don't think was ever really used for much