Scripts: remove tezos-docker-manager.sh

Context

In the changelog of Octez 13.0 (https://tezos.gitlab.io/CHANGES.html#docker-images), we wrote:

Breaking change: Script tezos_docker_manager.sh (also known as mainnet.sh) is now deprecated. It may be removed from Octez starting from version 14.0. It is recommended to write your own Docker Compose files instead. To this end, you can take inspiration from scripts/docker/docker-compose-generic.yml.

This MR removes tezos-docker-manager.sh.

Manually testing the MR

Check that you can't run tezos-docker-manager.sh? 🤔

Check for mentions of this script with git grep tezos-docker-manager.

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR