Remove enable welsh column

[thomasiles]

Remove the welsh_enabled column from the group table

Trello card: https://trello.com/c/gI4COCYo/2863-remove-welsh-feature-flag

The column has already been ignored so it should be safe to remove.

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[github-actions]

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