chore: synced file(s) with ecmwf-actions/reusable-workflows (#119)

* chore: created local '.github/pull_request_template.md' from remote 'sync-files/anemoi/some/.github/pull_request_template-core.md'

Triggered from common files on https://github.com/ecmwf-actions/reusable-workflows

* ci: clean up pr template folder

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Co-authored-by: VeraChristina <[email protected]>

Author: DeployDuck