Migration #6017 fails because 'selection_expression' column is too short

The step #6017, when upgrading from 9.0 or below, can fail if a portfolio has a selection expression, such as a regex, that is longer than 50 characters.

We fixed the column size in v9.2 with SONAR-15422 but it doesn't solve the problem with migrations.

The solution will be to change the migration #6015 so that it creates the new table with the correct column size.