Swap to pint for linting

[dbhynds]

Summary of Changes

Change our linter to pint, since that's the Laravel one and the one we use on the platform.

• [x] Depends on https://github.com/packbackbooks/lti-1-3-php-library/pull/121

Testing

• [x] I have added automated tests for my changes
• [x] I ran composer test before opening this PR
• [x] I ran composer lint-fix before opening this PR