Remove version from docker-compose.selenium.yaml

[penyaskito]

Fixes warns on ddev start.

This isn't software versions, but the spec version of a file that we only use on our environments.
And docker compose ignores this since v2, and always uses the latest spec available.

time="2024-12-03T19:23:04+01:00" level=warning msg="/home/penyaskito/Projects/Work/Lullabot/mjff/.ddev/docker-compose.memcached.yaml: the attribute `version` is obsolete, it will be ignored, please remove it to avoid potential confusion"
time="2024-12-03T19:23:04+01:00" level=warning msg="/home/penyaskito/Projects/Work/Lullabot/mjff/.ddev/docker-compose.selenium.yaml: the attribute `version` is obsolete, it will be ignored, please remove it to avoid potential confusion"
time="2024-12-03T19:23:04+01:00" level=warning msg="/home/penyaskito/Projects/Work/Lullabot/mjff/.ddev/docker-compose.solr.yaml: the attribute `version` is obsolete, it will be ignored, please remove it to avoid potential confusion"

File is at drainpipe-dev/scaffold/nightwatch/docker-compose.selenium.yaml

If the scaffolded file is committed to the repo and it's producing conflicts, a workaround is adding to composer.json:

"extra": {
    [...]
    "drupal-scaffold": {
        [...]
        "file-mapping": {
            "[project-root]/.ddev/docker-compose.selenium.yaml": false,
            [...]
        }
        [...]
    }
}