Remove multi select usage (#6004)

As per title!

Also, I'm removing an incorrect logic in the enum migration runner that
takes care of the case where we have no defaultValue but non nullable
which is not a valid business case.

packages/twenty-server/src/engine/workspace-manager/workspace-migration-runner/services/workspace-migration-enum.service.ts

@@ -49,10 +49,6 @@ export class WorkspaceMigrationEnumService {
         typeof enumValue !== 'string',
     );
 
-    if (!columnDefinition.isNullable && !columnDefinition.defaultValue) {
-      columnDefinition.defaultValue = serializeDefaultValue(enumValues[0]);
-    }
-
     const oldColumnName = `${columnDefinition.columnName}_old_${v4()}`;
 
     // Rename old column