Remove migrations squashed in v1.0

[mikkonie]

Remove migrations squashed in v1.0, see #1446.

Note: This will require the site to be deployed/migrated on v1.0 prior to upgrading an existing version to v1.1. This needs to be mentioned in the major changes documentation.

Tasks

• [ ] Remove squashed migrations from projectroles
• [ ] Remove squashed migrations from adminalerts
• [ ] Remove squashed migrations from bgjobs
• [ ] Remove squashed migrations from filesfolders
• [ ] Remove squashed migrations from sodarcache
• [ ] Remove squashed migrations from timeline
• [ ] Update major changes doc