Fix computation column change in the leaderboard

[ihsaan-ullah]

@ mention of reviewers

@Didayolo

A brief description of the purpose of the changes contained in this PR.

When updating leaderboard from the UI, changing removing computation from a column was not reflecting after saving the competition. This is now fixed.

Issues this PR resolves

• 1600

Checklist

• [x] Code review by me
• [x] Hand tested by me
• [x] I'm proud of my work
• [x] Code review by reviewer
• [x] Hand tested by reviewer
• [x] CircleCi tests are passing
• [x] Ready to merge