remove redundant scheduler_lock column from dag table

[prabhusneha]

closes: #42258

Remove all scheduler_lock references from the codebase.

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[boring-cyborg]

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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]

LGTM. One minor comment inline to remove the duplicate migration script.

[boring-cyborg]

Awesome work, congrats on your first merged pull request! You are invited to check our Issue Tracker for additional contributions.

[ephraimbuddy]

Congrats on your first PR @prabhusneha 🎉🎉