[FLI-978] Issue with latest mysql 8 release

[Mark Phelps]

From CI: https://github.com/flipt-io/flipt/actions/runs/8910246245/job/24469145698

-- Add foreign key constraint on namespace_key and segment_key columns referencing namespace_key and key columns of segments table
ALTER TABLE rules ADD FOREIGN KEY (namespace_key, segment_key) REFERENCES segments(`namespace_key`, `key`) ON DELETE CASCADE;
 (details: Error 1553 (HY000): Cannot drop index 'PRIMARY': needed in a foreign key constraint)

This seems to be a backward incompatible change with the latest release of MySQL 8 (8.0.37 2024-04-30, General Availability) that was released yesterday:

https://dev.mysql.com/doc/relnotes/mysql/8.0/en/news-8-0-37.html

_FLI-978