Don't hide Social Apps that weren't already hidden during migration

[LMNTL]

Checklist

1. If you've added code that should be tested, add tests
2. If you've changed APIs, update (or create!) the documentation
3. Ensure the tests pass
4. Make sure that your code lints and that you've followed our coding style
5. Write a title and, if necessary, a description of your work suitable for publishing in our release notes
6. Mention any related issues in this repository (as #ISSUE) and in other repositories (as kobotoolbox/other#ISSUE)
7. Open an issue in the docs if there are UI/UX changes

Notes

The migration in question would create a SocialAppCustomData for any Social App it touched, hiding some providers on the login page that shouldn't have been. Before the allauth update, OIDC providers could be configured fully from environment variables, which would leave them hidden - now, only those providers are hidden. This should reduce the number of manual steps necessary to migrate providers from env vars to the database.