Fix project job token scopes test

Adds a V0 → V1 state upgrader for gitlab_project_job_token_scopes so existing state written by the 18.x provider (which still had project_id) can be refreshed by
19.x without unsupported attribute "project_id". The upgrader copies the deprecated project_id (int64) into the new required project (string). Also drops the now-impossible "ImportState verify" step the migration test ran between the external 18.8 apply and the new-provider apply — state upgraders fire on
plan/refresh/apply, not on terraform show, so that step could never have worked. Migration is still exercised end-to-end by the following apply + ImportState steps.