ci: fix line breaks in check scripts and sanitize commit hash
- Updated .gitlab/templates/linting.yml to use YAML block scalars (|-) for all check scripts to avoid introducing leading spaces on line breaks.
- Added commit_hash.strip() in check_style.py and check_copyright.py to prevent accidental whitespace in Git arguments.
Signed-off-by: Wei-Chia Su Wei-Chia.Su@arm.com