Fix index issues in easyaudit migration files for compatibility with Django 4

[TheProlifical]

• Replaced deprecated index_together with indexes in the CRUDEvent model's Meta class.
• Updated migration files to use the new models.Index syntax for defining indexes.
• Resolved issues with missing or incorrectly defined indexes during the migration process.
• Ensured compatibility with the latest Django versions to prevent migration errors related to index handling.

[mschoettle]

Can you try out v1.3.7.rc2 (https://pypi.org/project/django-easy-audit/1.3.7rc2/). It has a fix for this already.

[TheProlifical]

It works! thanks!