Overwrite db.php before importing database

[grgar]

Ensure SQLite integration is in place since importing database reads file to determine version.

Related issues

• Fixes "Could not determine the version of the SQLite integration plugin" on pull of database from WordPress.com site #3518

How AI was used in this PR

This was my own work. I asked AI to investigate the problem from the issue and it made some random changes that didn't make any difference.

Proposed Changes

The database import reads SQLITE_DB_DROPIN_VERSION but which doesn't exist, because db.php got overwritten by the import as I have Query Monitor plugin installed on my WordPress.com site. Therefore, recreate db.php before importing the database (at the expense of Query Monitor no longer having its drop-in db.php active).

Testing Instructions

I only have one paid site (my personal site) on WordPress.com, so I tested by

1. Having Query Monitor installed on a site.
2. Pulling it into a new site created in Studio.
3. Error from "Could not determine the version of the SQLite integration plugin" on pull of database from WordPress.com site #3518 does not occur.

Pre-merge Checklist

• Have you checked for TypeScript, React or other console errors?