Migration runs on every request

[sebastian-lenz]

The plugin currently runs the latest migration on every request right in the init function, please see:

https://github.com/ethercreative/simplemap/blob/v3/src/SimpleMap.php#L48

I don't think this is intentional and looks like some accidentally commited test code. Furthermore, running a migration right here causes errors cause other plugins have not initialized yet and the migration cycles through all fields.