Remove migrations scripts for v9 -> v10 upgrades

[jennifer-shehane]

What would you like?

We'd like to remove the migration code in Cypress 15 that assists users from upgrading from v9 to v10 (with the migration screens to rename files, update config, etc.

Why is this needed?

This will remove code in our codebase, making it easier to maintain.

Other

If a user is doing an upgrade from v9 to v15 - they would not see this migration screen and it would not be an optimal experience. We're assuming that a lot of users would not be doing such a large upgrade and if users encounter this situation, we'd encourage them to install v10 first - run through the migration, then upgrade to a later version. (Preferably 1 major version at a time)

[jennifer-shehane]

The work for this is done and will be released in Cypress 15. We'll add a comment here once Cypress 15 is released.